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Abstract: Tensile behaviour plays a very significant role in the performance of cement-stabilized pavements under traffic, as well as under environmental loading. This paper reports the results of direct tensile [...]

As a load distributive compression anchor (LDCA) consists of multiple anchor bodies and unbonded tendons, the load applied to the tendon is transmitted to grout and ground by the movement of each anchor body installed along the anchor length. Therefore, the load transfer behavior of LDCA is affected by the interference between adjacent anchor body, and the effect of multiple anchor bodies should be considered in the LDCA design. This study performed a series of pull-out field tests on LDCAs installed in soft rock. LDCAs were designed to have various number and spacing of anchor bodies to investigate the effect of multiple anchor bodies. Furthermore, the test results were compared with the results of pull-out field tests conducted on weathered rock to examine the effect of ground conditions. The load-displacement relationship showed that the grout failure occurred in the LDCA installed in soft rock, and thus the ultimate bearing capacity was smaller than that of the LDCA installed in weathered rock. Additionally, the grout axial load distribution indicated that the LDCA installed in soft rock expressed tensile stress in the grout due to the effect of multiple anchor bodies leading to the tensile failure on the grout. Key words: ground anchor, load distributive compression anchor, load transfer mechanism, interference effect, pull-out field test, Introduction Ground anchors have been used on a variety of construction sites, including deep excavation, retaining wall, tunnels, and slope stabilization. Ground anchors transfer the load applied to the tendon [...]

Rigid piles (e.g., concrete piles) have been widely used to improve soft clay for the rapid construction of embankments. In this study, a damage plasticity model that considers the brittle failure behavior of concrete and the frictional properties along cracks is proposed to study the progressive failure of rigid piles under an embankment load. The mechanical characteristics of piles in different locations have been analyzed. The results show that the essential failure mode for rigid piles is tensile failure, which is primarily governed by the distribution of the bending moment and the axial force within the piles. Pile rupture releases stress and causes a significant increase in the tensile stress within neighboring piles, possibly leading to the progressive failure of adjacent piles. Failure in the upper section of piles ultimately leads to the propagation of a slip surface and the global failure of the embankment. The parametric analysis indicates that increases in the pile stiffness and the embankment load result in a higher tensile stress within the piles and a change in the failure mechanism from shear failure to bending failure. In addition, a failure envelope is proposed to determine the failure mode of the piles.Key words: embankment, rigid pile, post-failure behavior, progressive failure, stability.Des pieux rigides (par exemple, des pieux en beton) ont ete largement utilises pour ameliorer l'argile molle pour la construction rapide de remblais. Dans cette etude, un modele de plasticite des dommages qui considere le comportement de rupture fragile du beton et les proprietes de frottement le long des fissures est propose pour etudier la rupture progressive de pieux rigides sous une charge de remblai. Les caracteristiques mecaniques des pieux dans differents endroits ont ete analysees. Les resultats montrent que le mode de rupture essentiel pour les pieux rigides est la rupture a la traction, qui depend principalement de la repartition du moment de flexion et de la force axiale dans les pieux. La rupture du pieu libere la contrainte et provoque une augmentation significative de la contrainte a la traction dans les pieux voisins, ce qui peut entrainer une rupture progressive des pieux adjacents. La rupture dans la partie superieure des pieux mene finalement a la propagation d'une surface de glissement et a la rupture globale du remblai. L'analyse parametrique indique que l'augmentation de la rigidite du pieu et de la charge du remblai entraine une contrainte a la traction plus elevee a l'interieur des pieux et une modification du mecanisme de rupture allant de la rupture par cisaillement a la rupture par flexion. De plus, une enveloppe de rupture est proposee pour determiner le mode de rupture des pieux. [Traduit par la Redaction]Mots-cles : remblai, pieux rigides, comportement apres la rupture, rupture progressive, stabilite., 1. IntroductionEmbankments underlain by soft ground require a ground improvement technique to prevent instability and excessive settlement. Stone columns (e.g., Abusharar and Han 2011; Zhang et al. 2014b; Zhou et [...]

The influence of tensile strength on the behaviour of cohesionless soils is typically ignored in geotechnical engineering practice. However, the tensile cracking and subsequent failure characteristics of earth structures, such as dams, slopes and embankments, are significantly influenced by the tensile strength. For this reason, a semi-empirical model is proposed for predicting the variation of the tensile strength of unsaturated cohesionless soils with the degree of saturation, using the soil-water characteristic curve (SWCC) as a tool. The proposed model is capable of predicting the tensile strength arising from matric suction and surface tension, which are related to saturated pores and to the air-water interface associated with water bridges around interparticle contacts in unsaturated pores, respectively. Information about (i) the matric suction ([u.sub.a] - [u.sub.w]), the capillary degree of saturation ([S.sub.c]), and the residual degree of saturation ([S.sub.r]) derived from the SWCC; (ii) the mean particle size ([d.sub.50]) and the coefficient of uniformity ([C.sub.u]) from the grain-size distribution curve; (iii) the void ratio (e); and (iv) the friction angle ([[phi].sub.t]) at low normal stress level is required to employ this model. The proposed model is validated by comparing the prediction results with measured tensile strength of 10 different unsaturated cohesionless soils (including five sandy soils and five silty soils). The proposed model is promising for use in engineering practice applications as it only requires conventional soil properties, alleviating the need for cumbersome experimental studies for the determination of tensile strength of unsaturated cohesionless soils. Key words: tensile strength, unsaturated cohesionless soils, matric suction, surface tension, soil-water characteristic curve. L'influence de la resistance a la traction sur le comportement des sols non cohesifs est generalement ignoree dans la pratique de l'ingenierie geotechnique. Cependant, les caracteristiques de fissuration a la traction et de rupture subsequente des structures terrestres telles que les barrages, l'inclinaison et les digues sont influencees de maniere significative par la resistance a la traction. Pour cette raison, un modele semi-empirique est propose pour predire la variation de la resistance a la traction des sols non cohesifs insatures avec le degre de saturation, en utilisant la courbe caracteristique sol-eau (SWCC) comme un outil. Le modele propose est capable de predire la resistance a la traction resultant de la succion matricielle et de la tension superficielle qui sont liees a des interstitiels satures et a l'interface air-eau associee, aux ponts d'eau autour des contacts interparticulaires dans les interstitiels insatures, respectivement. L'information de (i) la succion matricielle ([u.sub.a] - [u.sub.w]), degre de saturation capillaire ([S.sub.c]), et le degre de saturation residuelle ([S.sub.r]) derive du SWCC; (ii) la taille moyenne des particules ([d.sub.50]) et le facteur d'uniformite ([C.sub.u]) de la courbe de distribution granulometrique; (iii) le taux de vide (e); et (iv) l'angle de frottement ([[phi].sub.t]) a un niveau de contrainte normal est requis pour utiliser ce modele. Le modele propose est valide en comparant les resultats de prediction avec la resistance a la traction de 10 sols non cohesifs insatures (y compris cinq sols sableux et cinq sols limoneux). Le modele propose est prometteur pour une utilisation dans les applications de la pratique d'ingenierie, car il ne necessite que des proprietes de sol conventionnelles, attenuant le besoin d'etudes experimentales encombrantes pour la determination de la resistance a la traction des sols non cohesifs insatures. [Traduit par la Redaction] Mots-cles : resistance a la traction, sol non cohesif insature, succion matricielle, tension superficielle, courbe caracteristique de l'eau souterraine., Introduction Tensile strength is a key property that significantly influences tensile cracking and subsequent tensile failure of earth structures, such as the earth dams, slopes, highway embankments, the clay covers [...]

The indirect tensile strengths (ITSs) of more than 200 disc specimens for 19 different rock and rock-like materials were determined by considering the concept of fracture toughness under different loading conditions. Steel loading arcs with various contact angles and flat platens were used in experiments to investigate whether they can be used as alternatives for the standard Brazilian jaw. Many of the disc specimens tested under the standard jaw did not fail with ideal tensile cracking at the centre, whereas simple splitting cracks were obtained along the vertical diameter of most of the discs tested under the flat platens. However, flat platens caused cracks to initiate in the compressive zone just under the loading points. This is an important outcome for criticizing the validity of the test because tensile failure is expected to occur along the vertical diameter of the disc. Friction conditions between the disc and jaw have important roles in the failing load. Moreover, fracture toughness is an additional parameter for investigating the ITSs of rock materials. According to the experimental results, fracture toughness values were found to increase with an increase in contact angle. In addition to the experimental study, finite element analyses were performed on several types of rock discs under various loading conditions. As a result, a comparison between all loading conditions was made to determine the best ITSs of the rocks. Both experimental and numerical analyses concluded that deciding the best loading type depends on the rock type. Therefore, the standard jaw is not recommended to use for determination of the ITS values of all rock types. Key words: tensile strength, indirect tensile strength test, splitting method, Brazilian test, loading apparatus, finite element analyses. On a determine la resistance a la traction indirecte (RTI) de plus de 200 specimens discoidaux composes de 19 types differents de materiaux rocheux ou d'aspect quasi rocheux en prenant en compte le concept de << tenacite >> dans differentes conditions de chargement. Des experiences ont ete realisees sur des arches de chargement en acier presentant differents angles de contact et sur des plateaux a surface plane pour savoir si ces arches et plateaux pouvaient remplacer le dispositif standard de compression par fendage. Un grand nombre des specimens discoidaux mis a l'essai a l'aide du dispositif standard de compression n'ont pas cede et comportaient une fissuration ideale de traction en leur centre, tandis qu'une simple fissuration le long du diametre vertical a ete observee sur la plupart des disques mis a l'essai a l'aide des plateaux a surface plane. On a constate que, lorsqu'on utilisait des plateaux a surface plane, les fissures prenaient naissance dans la zone de compression, situee juste en dessous des points d'application du chargement. Il s'agit d'une observation importante qui permet de critiquer la validite de l'essai realise, car on s'attend a ce que la rupture en traction se produise le long du diametre vertical du disque. Les frottements entre le disque et le dispositif de compression influent beaucoup sur la charge de rupture. De plus, la tenacite constitue un parametre supplementaire a prendre en compte lors de l'etude de la RTI de materiaux rocheux. D'apres les resultats experimentaux, on a observe que les valeurs de tenacite augmentaient avec l'angle de contact. Outre l'etude experimentale realisee, des analyses par la methode des elements finis ont ete effectuees sur plusieurs types de disques rocheux differents dans differentes conditions de chargement. On a pu ainsi comparer entre elles les differentes conditions de chargement afin de determiner la RTI optimale de chaque specimen. Des analyses experimentales et numeriques ont permis de conclure que le choix d'un type de chargement optimal dependait du type de roche mis a l'essai. Par consequent, il n'est pas recommande d'utiliser un dispositif standard de compression pour determiner la RTI, quel que soit le type de roche etudie. [Traduit par la Redaction] Mots-cles : resistance a la traction, essai de resistance a la traction indirecte, type de fissuration, essai de traction par fendage, dispositif de charge, analyses par la methode des elements finis., Introduction The Brazilian test is the most popular indirect tensile strength (ITS) test method because it can be used with conventional compressive test equipment (Hobbs 1964; Barla and Innaurato 1973). [...]

Volumetric behaviour is a fundamental consideration in unsaturated soil constitutive modelling. It is more complex than when the soil is saturated, as unsaturated soils exhibit a range of responses such as swelling and collapse under wetting and shrinkage and cracking during drying. While significant advances have been made, it is still difficult to generally explain all patterns of behaviour. This paper presents a new framework for modelling volumetric response of unsaturated soils with emphasis on compacted soils. The framework uses void ratio (e), moisture ratio ([e.sub.w]), and net stress (p) as the main constitutive variables and suction as a dependent variable. This choice of [e.sub.w] as a main constitutive variable is theoretically sound and is more attractive than the use of suction, which is relatively difficult to measure and displays significant hysteresis during drying and wetting. The framework incorporates the well-known compaction curve making it easily applicable to practical situations. Within the overall e-[e.sub.w]-p space, the operative space is constrained by three main surfaces; namely, loading-wetting state boundary surface, tensile failure surface, and the saturated plane. The conceptual basis for these state surfaces is described and the framework is qualitatively validated against observed behaviour of compacted soils. Key words: unsaturated soils, moisture content, soil compaction, void ratio, constitutive modelling. Le comportement volumetrique est une consideration fondamentale lors de la modelisation constitutive des sols non satures. La complexite est plus grande que lorsque le sol est sature puisque les sols non satures presentent une variete de comportements, comme le gonflement et l'effondrement durant le mouillage, et le retrait et la fissuration lors du sechage. Malgre le fait que plusieurs avancees significatives ont ete realisees, il est encore difficile d'expliquer de facon generale tous les types de comportement. Cet article presente une nouvelle approche pour la modelisation du comportement volumetrique des sols non satures, avec une emphase sur les sols compactes. L'approche utilise l'indice des vides (e), le ratio d'humidite ([e.sub.w]) et la contrainte nette (p) en tant de variables constitutives principales, et la succion en tant que variable dependante. Ce choix de [e.sub.w] comme variable constitutive principale est justifiable de maniere theorique et est plus simple que d'utiliser la succion, puisque la succion est relativement difficile a mesurer et demontre des effets d'hysteresis importants en mouillage et en sechage. Cette approche integre la courbe de compaction bien connue, ce qui la rend applicable aux situations pratiques. A l'interieur de l'espace e-[e.sub.w]-p, l'espace operatoire est contraint par trois surfaces principales: la surface frontiere de l'etat en mouillage-sechage, la surface de rupture en tension, et le plan sature. La base conceptuelle de ces trois surfaces est decrite et l'approche est validee qualitativement a l'aide d'observations du comportement de sols compactes. Mots-cles: sols non satures, teneur en eau, compaction du sol, indice des vides, modelisation constitutive. [Traduit par la Redaction], Introduction A large portion of geotechnical works is associated with unsaturated soil either as compacted fills or natural soil above the water table. In contrast to saturated soils below the [...]

This paper presents an integrated bearing capacity-settlement approach to the design of shallow foundations on heavily overconsolidated clays by alterations of the 'modified Cam clay' (MCC) model. The bearing capacity of soils and their settlements from loads imposed on shallow footings have been studied extensively. Yet, there is no consensus on a method that provides both reliable load-bearing capacity and settlement predictions. Current methods treat the soil under shallow footings as different ideal materials for the purpose of calculating the bearing capacity and settlement. The method proposed in this paper treats the soil as a single ideal material for both bearing capacity and settlement. The MCC model is tailored by adding Hvorslev's findings on overconsolidated clays and delineating stress states that bring the soil to tensile failure from those that cause it to yield or behave elastically or to show discontinuous response. A limiting stress surface is established as defining a limiting bearing capacity. A heavily overconsolidated clay is assumed to behave elastically if its stress state is below the limiting stress surface. Predictions from the method proposed in this paper compare favorably with model tests and field test results. Examples are provided illustrating how to use the proposed method. Key words: clays, critical state, Cam clay, foundation, footing, overconsolidated. Cet article presente une approche integree de capacite portante et tassement pour la conception de fondations peu profondes sur des argiles tres surconsolidees, basee sur le << modele argile de Cam modifie >> (ACM). La capacite portante des sols et leurs tassements causes par des charges imposees sur des semelles peu profondes ont ete largement etudies. Cependant, il n' y a pas de consensus sur une methode qui fourni des predictions fiables autant pour la capacite portante que le tassement. Les methodes courantes considerent le sol sous les semelles peu profondes comme differents materiaux ideaux pour realiser les calculs de capacite portante et de tassement. La methode proposee dans cet article considere le sol comme un seul materiau ideal pour la capacite portante et pour le tassement. Le modele ACM est ajuste par l' ajout des resultats de Hvorslev sur les argiles surconsolidees et sur la delimitation entre les etats des contraintes qui causent la rupture en tension du sol et ceux qui causent l' ecoulement ou le comportement elastique ou un comportement discontinu. Une surface de contrainte limite est etablie pour definir la capacite portante limite. Une argile tres surconsolidee est consideree comme ayant un comportement elastique si l'etat des contraintes est sous la surface de contrainte limite. Les predictions obtenues avec la methode proposee dans cet article se comparent bien avec les resultats des essais modelises et des essais sur le terrain. Des exemples pour illustrer l' application de la methode proposee sont presentes. Mots-cles : argiles, etat critique, argile de cam, fondation, semelle, surconsolide. [Traduit par la Redaction], Introduction The bearing capacity of soils under shallow foundations has been studied extensively (e.g., Terzaghi 1943; Meyerhof 1951, 1963, 1965; Hansen 1970; Vesic 1973). Terzaghi (1943) set the stage for [...]

To study creep failure behaviors of jointed rock mass with seepage pressure as the main damage driving force, creep tests under multi-level loading of seepage pressure were conducted on sandstone with different joint dip angles. In addition, a memory-dependent nonlinear seepage-creep model was established for jointed sandstone. The results show that jointed sandstone experiences three creep stages (initial, steady-state, and accelerated creep stages) in creep tests under multi- level loading paths of seepage pressure. Jointed sandstone with joint dip angles of 30[degrees] and 60[degrees] undergoes shear failure, while that with the joint dip angle of 45[degrees] is subject to tensile-shear failure. Under the same seepage pressure, the sandstone with the joint dip angle of 45[degrees] has a greater creep rate in the steady-state creep stage than that with joint dip angles of 30[degrees] and 60[degrees]. In the volumetric compression stage, the permeability increases at the instant of applying each level of seepage pressure, followed by gradual reduction and stabilization of permeability. In the volumetric dilation stage, the permeability gradually rises. The theory of memory-dependent derivative reflecting the time memory effect was introduced to establish the memory- dependent nonlinear viscoelastic-plastic seepage-creep model for jointed sandstone. The results obtained using the theoretical model conform to the test data. Moreover, the creep failure criterion of the rock was proposed. The creep acceleration starts to increase from 0 and the critical steady state transitions to a non-steady state, suggesting that the rock will soon be damaged. The calculation formula for critical time corresponding to the critical steady state of creep was also deduced. The critical time to onset of creep can serve as an early warning of the creep failure of rocks. Key words: multi-level loading of seepage pressure, jointed sandstone, creep, memory-dependent derivative, failure criterion, Introduction Deep rock engineering is constructed in an environment with high geostress and high seepage pressure (Zhang et al. 2021b; Zhang et al. 2022; Zhang et al. 2023a; Tan et [...]

Canada's recently active volcanic zones (e.g., eruptions during the past 10 000years) are all located along the tectonic plate boundary region of western Canada, extending for more than 2000 km from southern British Columbia to the Yukon/Alaska border. In this article, we describe the history of seismic monitoring in and near these volcanic zones and the past and current seismicity detection thresholds. The most recently active volcanoes in Canada are Tseax Cone (~1700s) and Lava Fork (~1800s), both in northwestern British Columbia. However, no eruptions have occurred in Canada since the deployment of the earliest seismographs in 1898 (Victoria, BC) and 1904 (Sitka, Alaska). Seismic detection levels have decreased from M~7 in 1900 to M~0-1 (in many regions) today, with more than 120 seismic stations currently operating in British Columbia and the Yukon, including ~20 seismic stations within the volcanic zones. The most recent significant seismic activity attributed to volcanic zones in Canada is the 2007 Nazko Cone earthquake swarm when nearly 1000 tiny (M < 3) earthquakes occurred here over the span of about 2 months. These were all deep earthquakes (~30 km) near the base of the crust and showed the patterns expected from an injection of magma deep into the crust. Prior to that, at the western end of the Anahim Volcanic Belt, more than 40 felt earthquakes occurred from 1940 to 1943. We provide a summary of these two swarms and other seismicity as well as some recent and ongoing studies into seismicity at some of Canada's volcanic zones and new developments in seismic monitoring of volcanoes (including using distributed acoustic sensing). Key words: seismicity, seismic monitoring, volcanic seismicity, seismic hazards, Introduction The west coast of North America is a region of active plate tectonics, where the Pacific plate meets the North American plate off the coast of British Columbia, and [...]

Microwave energy is a promising application in future rock breakage operations in the civil, mining, processing, and space industries. Rock engineering projects frequently experience mechanical vibration and blasting impacts. Thus, understanding the dynamic fracturing behavior of microwave-treated rock is essential for its future application in microwave-assisted mechanical rock breakage. A customized industrial microwave system with a multimode resonant cavity was used to heat red sandstone at different microwave power levels (up to 4 kW) for a constant exposure time (4 min). The rock surface temperature distribution after microwave treatment was measured by an infrared camera. Dynamic splitting tests were conducted using a split Hopkinson pressure bar (SHPB) system in combination with a high-speed camera. Experimental results indicate that the rock dynamic splitting strength is negatively related to the microwave power, and the maximum reduction is 47.8%. Microwave treatment induced an obvious nonuniform temperature distribution and C-shaped surface cracks on disc specimens. During the dynamic splitting test, the crack induced by dynamic loading always initiates from the crack tip induced by microwave irradiation and then propagates along the loading diameter. The distribution of the inner high-temperature zone in the disc specimen is symmetric along the horizontal centerline of the disc specimen. Key words: microwave treatment, dynamic splitting behavior, infrared temperature, rock fracturing, dynamic nominal tensile strength. Le recours a l'energie micro-ondes represente un potentiel prometteur dans les futures operations de bris de roche dans les industries civiles, minieres, de transformation et spatiales. La vibration mecanique et les impacts des explosions sont frequents dans les projets d'ingenierie des roches. Il est donc essentiel de comprendre le comportement dynamique de fracturation de la roche traitee par micro-ondes pour son application future dans les operations de rupture mecanique de la roche assistee par micro-ondes. On a utilise un systeme micro-ondes industriel personnalise equipe d'une cavite resonnante multimode afin de chauffer du gres rouge a differents niveaux de puissance micro-ondes (jusqu'a 4 kW) durant un temps d'exposition constant (4 min). La distribution de la temperature de la surface de la roche apres le traitement par micro-ondes a ete mesuree par une camera infrarouge. Des essais de fendage dynamique ont ete realises a l'aide d'un systeme de barre de pression Hopkinson fendue (SHPB) associe a une camera a grande vitesse. Selon les resultats experimentaux, la limite de fendage dynamique de la roche est negativement liee a la puissance des micro-ondes, et la reduction maximale est de 47,8 %. Le processus de traitement par micro-ondes a provoque une distribution non uniforme de la temperature et des fissures superficielles en forme de C sur les specimens de disques. Pendant l'essai de fendage dynamique, la fissure induite par le chargement dynamique commence toujours a partir de la pointe de la fissure induite par l'irradiation par micro-ondes, puis se propage le long du diametre de chargement. La distribution de la zone interne a haute temperature du specimen de disque est symetrique le long de la ligne centrale horizontale du specimen de disque. [Traduit par la Redaction] Mots-cles: traitement par micro-ondes, comportement dynamique de fendage, temperature infrarouge, fracturation de la roche, resistance nominale dynamique a la traction., 1. Introduction Safe and efficient continuous rock breakage significantly affects the progress of rock engineering projects. As the most commonly used rock breakage technique, drilling and blasting have been widely [...]

This study aimed to quantitatively identify the influence of the block impact angle and block shape on the impact effect of reinforced concrete (RC) sheds. The smooth particle hydrodynamic (SPH) method and finite element method (FEM) were coupled and used to solve the simulation difficulty of large deformation of the sand buffer layer in the RC shed. SPH was used to simulate the sand buffer layer in the impact area that experienced large deformation. Concrete, reinforced, bedrock, block and sand buffer layer in the non-impact area were simulated by FEM. The accuracy of the coupled model was verified by the full-scale test data. Finally, the impact forces and the dynamic responses of the RC shed were analyzed, focusing on the effects of the block impact angle and shape. The numerical results show that the coupled SPH-FEM method is effective for simulating how block impacts the RC shed. The block impact angle and shape can significantly influence the normal and tangential impact forces. The design of the RC shed based on the assumption of blocks as free-falling spherical projectiles can lead to inaccuracy in some impact scenarios, and an appropriate correction was put forward in available empirical calculating formulae to include the effect of the irregular shape and impact angle of the block. The sand buffer layer dissipates a large part of the energy, which accounts for at least 58% of the initial impact energy. Key words: rockfall impact angle, rockfall shape, reinforced concrete shed, coupled SPH-FEM model, impact effect. Cette etude visait a determiner quantitativement l'influence de l'angle d'impact et de la forme du bloc sur l'effet d'impact des pare-pierres en beton arme (BA). La methode de l'hydrodynamique des particules lisses (HPL) et la methode des elements finis (MEF) ont ete couplees et utilisees pour resoudre la difficulte de simulation de la deformation importante de la couche tampon de sable dans le pare-pierres en BA. L'HPL a ete utilisee pour simuler la couche tampon de sable dans la zone d'impact qui a subi une deformation importante. Le beton, le beton arme, le substrat rocheux, le bloc et la couche tampon de sable dans la zone non touchee ont ete simules par la MEF. La precision du modele couple a ete verifiee par les donnees d'essai a grande echelle. Enfin, les forces d'impact et les reponses dynamiques du pare-pierre en BA ont ete analysees, en se concentrant sur les effets de l'angle d'impact et de la forme du bloc. Les resultats numeriques montrent que la methode couplee HPL-MEF est efficace dans la simulation de l'impact du bloc sur le pare-pierres en BA. L'angle d'impact et la forme du bloc peuvent exercer une influence significative sur les forces d'impact normales et tangentielles. La conception du pare-pierres en BA basee sur l'hypothese de blocs comme projectiles spheriques en chute libre peut entrainer des imprecisions dans certains scenarios d'impact, et une correction appropriee a ete proposee dans les formules de calcul empiriques disponibles afin d'inclure l'effet de la forme irreguliere et de l'angle d'impact du bloc. La couche tampon de sable dissipe une grande partie de l'energie, qui represente au moins 58 % de l'energie d'impact initiale. [Traduit par la Redaction] Mots-cles : angle d'impact de chute de roches, forme de chute de roches, pare-pierres en beton arme, modele HPL-MEF couple, effet d'impact., 1. Introduction Rockfall is a type of natural hazard that involves detachment of rock blocks from a steep slope or cliff, followed by rapid down-slope movements as characterized by freefall, [...]

When an extreme internal loading is applied to prestressed concrete (PSC) structures, serious property damage and human casualties may occur. However, the existing designs for PSC structures such as prestressed concrete containment vessels (PCCVs) do not include features to protect the structure from forces such as explosive blasts. Therefore, we evaluated the internal blast-resistance of PSC structures using blast tests on bi-directionally prestressed tubular concrete members. The goal of the study was to examine structural behavior data after an internal detonation. Explosive charges (ammonium nitrate--fuel oil; ANFO) were detonated at the center of the mid-span of the concrete tube with a standoff distance of 1000 mm. The data acquired included blast pressure, deflection, strain, crack pattern, and prestressing loss. The data were used to calculate the internal blast charge weight required to cause a PCCV to fail and to calibrate a simulation program to be used commercially for internal blast simulations at real scale structure. Key words: internal blast, prestressed concrete, PCCV, explicit finite element. Lorsque des charges extremes provenant d'une explosion interne sont appliquees a des structures en beton precontraint (BP), des dommages materiels graves et des pertes humaines peuvent survenir. Toutefois, les conceptions actuelles des structures de BP, comme les enceintes de confinement en beton precontraint (ECBP), ne comprennent pas de dispositifs pour proteger la structure contre les explosions. Par consequent, la capacite de resistance des structures en BP aux explosions internes a ete evaluee par des essais d'explosion interne sur des elements tubulaires BP bidirectionnels. L'objectif de l'etude etait d'obtenir les donnees sur le comportement structurel provenant d'une detonation interne. Les charges de l'ANFO ont ete declenchees au centre de la mi-portee de l'echantillon tubulaire avec une distance de securite de 1000 mm. Les donnees acquises comprenaient la pression de l'explosion, la deflexion, la deformation, le profil de fissure et la perte de precontrainte. Les donnees ont ete utilisees pour deriver les equations afin de calculer le poids de charge interne requis pour faire faillir une ECBP reelle et pour etalonner un programme de simulation commerciale a utiliser pour les simulations d'explosions internes. [Traduit par la Redaction] Mots-cles : explosion interne, beton precontraint, enceintes de confinement en beton precontraint (ECBP), element fini explicite., Introduction Prestressed concrete containment vessels (PCCVs) are built as bi-directional prestressed concrete (PSC) structures. They have improved stiffness and strength compared with reinforced concrete (RC); however, PSC is relatively brittle, [...]

Estimation of crack depths and spacing due to desiccation of clayey soils is needed to predict changes in mechanical or hydraulic properties in the cracked layer. These changes affect the infiltration of water, stability, and deformation of a soil mass. Desiccation cracks are associated with increasing suction due to moisture loss accompanied by restrained shrinkage, which results in tensile stresses in near surface soil layers. Cracks propagate when the developed tensile stresses exceed the tensile strength of soil. A simple analytical method is presented to predict crack depths in compacted clayey soil due to changes in matric suction with depth. The model equation is based on the Hookean elastic equation relating incremental strain to incremental stress and incorporates two stress state variables including net normal stress and matric suction. Input to the model equation includes the tensile strength and elastic parameters, and to complete the prediction of crack depth, the suction change profile of interest is needed. The method validity was investigated by comparing predicted crack depths to those observed in soil compacted in a bench scale apparatus for studying desiccation cracking. Tensile strength and elastic properties were determined from tests conducted on soil during desiccation under approximate uniaxial conditions. Predicted crack depths were obtained based on changes in suction interpreted from water content sensors at various depths in the soil bed and compared favorably to observed desiccation crack depths. Key words: desiccation cracks, tensile strength, matric suction, moisture loss, crack depth. L'estimation de la profondeur et de l'espacement des fissures dues a la dessiccation des sols argileux est necessaire pour prevoir les changements des proprietes mecaniques ou hydrauliques dans la couche fissuree. Ces changements affectent l'infiltration de l'eau, la stabilite et la deformation d'une masse de sol. Les fissures de dessiccation sont associees a une augmentation de la succion due a la perte d'humidite accompagnee d'un retrait limite, ce qui entraine des contraintes de traction dans les couches de sol proches de la surface. Les fissures se propagent lorsque les contraintes de traction developpees depassent la resistance a la traction du sol. Une methode analytique simple est presentee pour predire la profondeur des fissures dans un sol argileux compacte en raison des changements de la succion matricielle avec la profondeur. L'equation du modele est basee sur l'equation elastique de Hookean qui relie la deformation incrementale a la contrainte incrementale et incorpore deux variables d'etat de contrainte, a savoir la contrainte normale nette et la succion matricielle. L'entree de l'equation du modele comprend la resistance a la traction et les parametres elastiques, et pour completer la prediction de la profondeur de la fissure, le profil de changement de succion d'interet est necessaire. La validite de la methode a ete etudiee en comparant les profondeurs de fissures predites a celles observees dans un sol compacte dans un appareil en banc d'essai pour etudier la fissuration par dessiccation. La resistance a la traction et les proprietes elastiques ont ete determinees a partir d'essais realises sur le sol pendant la dessiccation dans des conditions uniaxiales approximatives. Les profondeurs de fissures predites ont ete obtenues sur la base des changements de succion interpretes a partir de capteurs de teneur en eau a differentes profondeurs dans le lit du sol et ont ete comparees favorablement aux profondeurs de fissures de dessiccation observees. [Traduit par la Redaction] Mots-cles : fissures de dessiccation, resistance a la traction, succion matricielle, perte d'humidite, profondeur de la fissure., Introduction Desiccation cracks due to soil shrinkage create substantial challenges in many geotechnical engineering scenarios where infiltration of water into a soil mass is undesirable, such as for landfill liners [...]

Pendulum impact tests were conducted on a reinforced concrete (RC) frame column and four RC free-standing columns. The effects of the axial compression ratio and reinforcement ratio on the impact resistance of the columns were compared using the dynamic time curves of framed and freestanding columns under impact. The test results show that for the same impact load, although the presence of axial loads can play a positive role (e.g., reducing the residual displacement), it may lead to more severe local damage. In addition, compared with free-standing columns, frame columns can be considered as a protective structure because of their greater lateral stiffness and stronger crashworthiness. The corresponding finite element models are developed, and the influence of the axial loads on the cross-section force responses under impact excitation was deeply explored. Axial loads can significantly affect the distribution of moment, shear force, and damage to the column. Key words: pendulum test, frame column, axial load effects, failure mode, numerical simulation. Des essais par choc a pendule ont ete effectues sur un poteau d'ossature en beton arme (BA) et quatre poteaux independants en BA. L'effet du taux de compression axiale et le pourcentage d'armature sur la resistance aux chocs des poteaux a ete compare au moyen de courbes de temps dynamiques de poteaux d'ossature et autoportants sous impact. Les resultats des essais montrent qu'avec la meme force de choc, bien que la presence de charges axiales puisse jouer un role positif (par exemple, reduire le deplacement residuel), elle peut entrainer des dommages locaux plus graves. De plus, par rapport aux poteaux autoportants, le poteau d'ossature peut etre considere comme une structure protectrice en raison de sa plus grande rigidite laterale et de sa plus grande resistance aux chocs. Les modeles d'elements finis correspondants sont developpes et l'effet des charges axiales sur les reponses de la force de section transversale sous l'excitation d'impact est explore en profondeur. Les charges axiales peuvent avoir une incidence significative sur la repartition des moments, la force de cisaillement, ainsi que les dommages pour le poteau. [Traduit par la Redaction] Mots-cles: essai pendulaire, poteau d'ossature, effets de charge axiale, mode de defaillance, simulation numerique., Introduction As a typical axial load-carrying structure in bridge piers and offshore buildings, reinforced concrete (RC) columns can suffer from lateral impact loads during vessel or vehicle collisions. Numerous catastrophic [...]

Timber-concrete composite is an efficient hybrid construction material that exploits the advantageous properties of timber and concrete. The use of shear connectors enables the two dissimilar materials to act together, resulting in an increase in global stiffness as well as load-carrying capacity. As this composite material is becoming increasingly more popular in the construction industry, there is a need to develop analysis tools that have general applicability to timber- concrete composite systems with variations in loading schemes, specimen configurations, materials, and types of shear connectors. One such tool, a generic two-dimensional nonlinear finite element model, is proposed in this paper; it is verified through numerical simulations of six experiment series carried out by other researchers. Good agreement between experimentally observed behaviour and numerical simulations was generally obtained. Key words: timber-concrete composite, shear connectors, structures, modelling, finite element analysis. Le composite bois-beton est un materiau de construction hybride efficace qui exploite les proprietes avantageuses du bois et du beton. L'utilisation de connecteurs de cisaillement permet aux deux materiaux dissemblables d'agir ensemble, entrainant une augmentation de la rigidite globale ainsi que de la portance. Comme ce materiau composite est de plus en plus populaire dans l'industrie de la construction, il est necessaire de developper des outils d'analyse qui sont generalement applicables aux systemes composites bois-beton avec des variations dans les schemas de chargement, les configurations de specimens, les materiaux et les types de connecteurs de cisaillement. L'un de ces outils, un modele des elements finis non lineaires non bidimensionnels generique, est propose dans cet article; il est verifie par des simulations numeriques de six series d'experiences realisees par d'autres chercheurs. On a generalement obtenu une bonne concordance entre le comportement observe experimentalement et les simulations numeriques. [Traduit par la Redaction] Mots-cles: composite bois-beton, connecteurs de cisaillement, structures, modelisation, analyse des elements finis., Introduction Timber-concrete composite (TCC) systems have seen increased development in the past two decades, finding extensive structural applications, including renovation and upgrading of existing timber structures, new construction of mid- [...]

The quality of cement-treated soil columns is normally assured based on the unconfined compressive strength [q.sub.u] of core samples. [q.sub.u] of core samples varies spatially and the statistical parameters of [q.sub.u] (i.e., mean [[mu].sub.qu], variance [[sigma].sup.2.sub.qu], and autocorrelation distance [[theta].sub.qu]) are adopted in quality assurance procedures. The statistical parameters of [q.sub.u] evaluated from the core sample strengths have a statistical uncertainty depending on the statistical sample size. The present study investigates the influence of the statistical sample size on the evaluation of overall strength of a cement-treated soil column. A probabilistic framework in which a Bayesian inference analysis and a finite element method analysis are incorporated is used to calculate the overall strength while simultaneously considering the statistical uncertainty and spatial variability of core strength. The probabilistic framework is briefly described, and a parametric analysis is performed to investigate the influence of the statistical sample size on the evaluation of the overall strength of a full-scale column. The numerical results show that the sample size and spatial correlation influence the variability of the overall strength, and the influence can be reasonably described using an equivalent number of independent data. Key words: cement-treated soil, strength, statistical sample size, statistical uncertainty, spatial variability. La qualite des colonnes de sol traitees au ciment est normalement assuree sur la base de la resistance a la compression non confinee [q.sub.u] des carottes. [q.sub.u] des carottes varie dans l'espace et les parametres statistiques des [q.sub.u] (c'est-a-dire moyenne [[mu].sub.qu], variance [[sigma].sup.2.sub.qu] et distance d'autocorrelation [[theta].sub.qu]) sont adoptees dans les procedures d'assurance qualite. Les parametres statistiques de [q.sub.u] evalues a partir des resistances des echantillons ont une incertitude statistique qui depend de la taille de l'echantillon statistique. La presente etude examine l'influence de la taille de l'echantillon statistique sur l'evaluation de la resistance globale d'une colonne de sol traitee au ciment. Un cadre probabiliste dans lequel une analyse d'inference bayesienne et une analyse par la methode des elements finis sont incorporees est utilise pour calculer la resistance globale tout en tenant compte simultanement de l'incertitude statistique et de la variabilite spatiale de la resistance des carottes. Le cadre probabiliste est brievement decrit et une analyse parametrique est realisee pour etudier l'influence de la taille de l'echantillon statistique sur l'evaluation de la resistance globale d'une colonne en vraie grandeur. Les resultats numeriques montrent que la taille de l'echantillon et la correlation spatiale influencent la variabilite de la resistance globale, et que cette influence peut etre raisonnablement decrite en utilisant un nombre equivalent de donnees independantes. [Traduit par la Redaction] Mots-cles: sol traite au ciment, resistance, taille de l'echantillon statistique, incertitude statistique, variabilite spatiale., Introduction The deep cement mixing method is a ground improvement technology in which cement is mixed with in situ soil. Ground improvements via deep mixing have been used for several [...]

The behaviour of squat shape partially grouted concrete masonry shear walls with fixed-end boundary conditions subjected to constant average axial stress and cyclic lateral loading was investigated. Two replicas were tested of each combination of horizontal reinforcement ratio (0.12%, 0.06%, and 0.03%) and four end anchorage conditions (straight, 90[degrees], 180[degrees], and shear studs). The behaviour of the walls was compared in terms of strength, ductility, stiffness, and dissipated energy. While the effect of horizontal bar size was greater than that of end anchorage, neither improved end anchorage nor smaller bar size increased yielding at critical locations on the rebars. The highest course of the wall should be reinforced and grouted, as that improves performance of the walls. In addition, the amount of horizontal reinforcement did not significantly affect the strength of the shear walls, therefore changes to the shear design equations in the Canadian Standard are recommended. Key words: partially grouted concrete masonry shear wall, diagonal shear failure, strength, bond beams, horizontal reinforcement, end anchorage conditions, cyclic in-plane loading, fixed end boundary conditions, shear wall design equation. On a etudie le comportement de murs en maconnerie de beton partiellement liaisonnee par injection de forme carree avec des conditions limites d'encastrement aux deux extremites soumises a une contrainte axiale moyenne constante et a une charge laterale cyclique. Deux repliques ont ete mises a l'essai pour chaque combinaison de taux d'armature horizontale (0,12, 0,06 et 0,03 %) et de quatre conditions d'ancrage aux extremites (goujons droits, 90[degrees], 180[degrees] et de cisaillement). Le comportement des murs a ete compare compte tenu de la resistance, de la ductilite, de la rigidite et de l'energie dissipee. Bien que l'effet de la taille des barres horizontales ait ete plus important que celui de l'ancrage aux extremites, ni l'ancrage aux extremites ameliore ni la taille plus petite des barres n'ont augmente la limite elastique a des endroits critiques sur les barres d'armature. Le plus haut plan du mur doit etre arme et injecte, car ceci ameliore la performance des murs. De plus, l'intensite de l'armature horizontale n'a pas eu d'incidence importante sur la resistance desmurs de contreventement; par consequent, il est recommande de modifier les equations de conception du cisaillement dans la norme canadienne. [Traduit par la Redaction] Mots-cles : mur de contreventement en maconnerie partiellement liaisonnee par injection, rupture diagonale par cisaillement, resistance, poutres de maconnerie, armature horizontale, conditions d'ancrage aux extremites, charge cyclique dans le plan, conditions limites d'encastrement aux deux extremites, equation de conception de mur de contreventement., 1. Introduction In modern masonry buildings, the lateral load resisting system usually comprises reinforced masonry shear walls. To increase the in-plane shear capacity, horizontal reinforcement is placed in such walls, [...]

This paper presents an interpretation technique to quantify the effects of compaction state and matric suction on the undrained shear strength of compacted clay under confined undrained triaxial compression. This novel technique is based on the mathematical frameworks of the 'stress history and normalized soil engineering property' (SHANSEP) method for saturated soil and the 'Barcelona basic model' (BBM) for unsaturated soil. Test data of compacted Calgary till were analyzed and interpreted using the proposed technique. The interpretation technique is very useful in delineating the relative impacts of the factors on the behavioural trends in measured undrained shear strength. It was found that in addition to the initial compacted void ratio and suction, soil structure and failure mode exert significant influence on the undrained shear strength of compacted clay. This technique is attractive to engineering practitioners because the confined undrained compression tests (with no pore-air and pore-water pressure measurement) are much simpler and less time-consuming compared to rigorous laboratory tests on unsaturated soil. Key words: compacted clay, undrained shear strength, suction, soil structure, tensile rupture, strain softening, ductile yielding. Cet article presente une technique d'interpretation permettant de quantifier les effets de l'etat de compactage et de la succion matricielle sur la resistance au cisaillement non drainee de l'argile compactee sous compression triaxiale confinee non drainee. Cette nouvelle technique est basee sur les cadres mathematiques de la methode SHANSEP ([musch less than] stress history and normalized soil engineering property [much greater than]) pour les sols satures et BBM ([musch less than] Barcelona basic model[much greater than]) pour les sols non satures. Les donnees d'essai du till compacte de Calgary ont ete analysees et interpretees a l'aide de la technique proposee. La technique d'interpretation est tres utile pour delimiter les impacts relatifs des facteurs sur les tendances comportementales de la resistance au cisaillement mesuree sans contrainte. Il a ete constate qu'en plus de l'indice des vides initial et de la succion initiale de l'argile compactee, la structure du sol et le mode de defaillance exercent une influence significative sur la resistance au cisaillement non drainee de l'argile compactee. Cette technique est attrayante pour les ingenieurs car les tests de compression confinee non drainee (sans mesure de la pression de l'air interstitiel et de l'eau interstitielle) sont beaucoup plus simples et moins longs que les tests rigoureux en laboratoire sur des sols non satures. [Traduit par la Redaction] Mots-cles : argile compactee, resistance au cisaillement non drainee, succion, structure du sol, rupture a la traction, ramollissement par contrainte, deformation ductile., Introduction The undrained shear strength, [s.sub.u], of saturated soil is one of the key input parameters in total stress analysis for short-term stability and capacity of geotechnical structures (e.g., shallow [...]

Understanding the strength and failure modes of overburdens and reservoirs is a critical component in safety assessments for oil sands surface mining and in situ thermal recovery operations. Currently, assumptions of homogeneity are often made for the geomechanical properties of oil sands in conventional slope stability analyses and reservoir simulation. The purpose of this work is to propose a numerical characterization workflow that helps predict the failure mode and shear strength of heterogeneous oil sands interbedded with shale beddings during thermal recovery. Heterogeneous models are generated through sequential indicator simulation with a calibrated constitutive model and geomechanical parameters for each lithology. Numerical simulations with boundary conditions reflecting in situ stress changes are conducted to study the impact of shale beddings on stress-strain response, failure modes, and shear strength of the sheared zone. The results show that shear failures of the weaker shale beddings play a significant role in the elastoplastic behavior and reduced shear strength of heterogeneous oil sands. The shear band and weak plane failures are found to be closely related to the volume fraction, variogram range ratio, and inclinations of shale beddings. The proposed numerical workflow allows for quantitative investigations of geomechanical response for rock mass with complex lithological heterogeneities. Key words: geomechanical characterization, heterogeneity, failure modes, shear strength, oil sands. La comprehension de la resistance et des modes de defaillance des morts-terrains et des reservoirs est un element essentiel des evaluations de la securite pour l'exploitation des sables bitumineux en surface et les operations de recuperation thermique in situ. Actuellement, des hypotheses d'homogeneite sont souvent formulees pour les proprietes geomecaniques des sables bitumineux dans les analyses classiques de stabilite des pentes et les simulations de reservoirs. L'objectif de ce travail est de proposer un flux de caracterisation numerique qui aide a predire le mode de defaillance et la resistance au cisaillement des sables bitumineux heterogenes interstratifies avec des couches de schiste pendant la recuperation thermique. Des modeles heterogenes sont generes par simulation d'indicateurs sequentiels avec un modele constitutif calibre et des parametres geomecaniques pour chaque lithologie. Des simulations numeriques avec des conditions limites refletant les changements de contraintes in situ sont realisees pour etudier l'impact des couches de schiste sur la reponse contraintedeformation, les modes de defaillance et la resistance au cisaillement de la zone cisaillee. Les resultats montrent que les ruptures de cisaillement des couches de schiste les plus faibles jouent un role important dans le comportement elastoplastique et la reduction de la resistance au cisaillement des sables bitumineux heterogenes. Il s'avere que la bande de cisaillement et les ruptures de plans faibles sont etroitement liees a la fraction volumique, au rapport de gamme des variogrammes et aux inclinaisons des couches de schiste. Le flux de travail numerique propose permet des etudes quantitatives de la reponse geomecanique pour des masses rocheuses presentant des heterogeneites lithologiques complexes. [Traduit par la Redaction] Mots-cles : caracterisation geomecanique, heterogeneite, modes de defaillance, resistance au cisaillement, sables bitumineux., 1. Introduction Oil sands are naturally occurring mixtures of sand, clay, water, and bitumen, estimated at 162.5 billion barrels occupying 96% of proven oil reserves in Canada (Natural Resources Canada [...]

This paper demonstrates reliability-based design (RBD) and analysis for tensile strength (rupture) and pullout limit states for mechanically stabilized earth (MSE) walls constructed with steel grid reinforcement in combination with frictional soils. Five different reinforcement tensile load models for walls under operational conditions are considered in combination with six different pullout models and one tensile strength model. The general approach considers the accuracy of the load and resistance models that appear in each limit state equation plus uncertainty in the choice of nominal values at the time of design that is linked to the concept of 'level of understanding' used in Canadian load and resistance factor design (LRFD) foundation engineering practice. The effect of potential steel corrosion on reliability index for the tensile strength limit state is considered in calculations. A well-documented MSE wall case study is used to demonstrate the general approach. The relationship between nominal factor of safety and reliability index is used to demonstrate how to optimize steel grid member diameters and arrangement to achieve a target reliability index of [beta] = 2.33. The approach described in this paper is an important contribution to next-generation analysis and design using modern concepts of RBD for MSE walls. Key words: reliability-based design (RBD), mechanically stabilized earth (MSE) walls, steel grid reinforcement, internal stability limit states. Cet document demontre la conception basee sur la fiabilite (CBF) et l'analyse de la resistance a la traction (rupture) et des etats limites d'arrachement pour les murs en terre stabilisee mecaniquement (TSM) construits avec un renforcement de grille en acier en combinaison avec des sols de friction. Cinq modeles differents de charge de traction des armatures pour les murs dans des conditions operationnelles sont consideres en combinaison avec six modeles d'arrachage differents et un modele de resistance a la traction. L'approche generale tient compte de la precision des modeles de charge et de resistance qui apparaissent dans chaque equation d'etat limite plus l'incertitude dans le choix des valeurs nominales au moment de la conception qui est liee au concept de << niveau de comprehension >> qui est utilise dans la pratique canadienne d'ingenierie des fondations en matiere de conception des facteurs de charge et de resistance (CFCR). L'effet de la corrosion potentielle de l'acier sur l'indice de fiabilite pour l'etat limite de resistance a la traction est pris en compte dans les calculs. Une etude de cas bien documentee sur le mur des TSM est utilisee pour demontrer l'approche generale. La relation entre le facteur nominal de securite et l'indice de fiabilite est utilisee pour demontrer comment optimiser le diametre et la disposition des elements de la grille en acier afin d'atteindre un indice de fiabilite cible de [beta] = 2,33. L'approche decrite dans ce document est une contribution importante a l'analyse et a la conception de la prochaine generation utilisant les concepts modernes de CBF pour les murs des TSM. [Traduit par la Redaction] Mots-cles : conception basee sur la fiabilite (CBF), murs en terre stabilisee mecaniquement (TSM), renforcement de la grille en acier, etats limites de stabilite interne., 1. Introduction This paper is focused on reliability-based design (RBD) and analysis for tensile strength and pullout limit states of steel grid-reinforced mechanically stabilized earth (MSE) walls constructed with frictional [...]

The behavior of the asphalt mixture is mainly attributed to the performance of the asphalt mastic. Several studies have been performed to evaluate the behavior of mastics made with different fillers. Most researchers have added the filler by mass within the bitumen; however, this comparison may be more appropriate by volume. An experimental program was designed to evaluate the behavior of mastics produced with five different fillers (natural limestone, LS; hydrated lime, HL; Portland cement, PC; Linz-Donawitz steel slag, LDSS; and blast furnace slag, BFS), and were dosed by mass and volume. Penetration, softening point, viscosity, multiple stress creep and recovery test, and linear amplitude sweep test were performed. Results showed that analyzed asphalt mastic properties depend on dosage type performed and test type. Furthermore, HL, PC, BFS and LDSS mastics showed better performance compared to control LS mastic. Key words: asphalt mastic, filler, mass and volume dosage, rheological properties. Le comportement du melange d'asphalte est principalement attribuable a la performance du mastic d'asphalte. Plusieurs etudes ont ete realisees afin d'evaluer le comportement des mastics fabriques avec differents produits de remplissage. La plupart des chercheurs ont ajoute le produit de remplissage par poids dans le bitume; toutefois, cette comparaison peut etre plus appropriee par volume. Un programme experimental a ete concu afin d'evaluer le comportement des mastics produits avec cinq produits de remplissage differents (calcaire naturel, LS; chaux hydratee, HL; ciment de Portland, PC; laitier d'acier de Linz-Donawitz, LDSS et laitier de haut fourneau, BFS) et ont ete doses par poids et par volume. La penetration, le point de ramollissement, la viscosite, l'essai de fluage et de recuperation a contraintes multiples et l'essai de balayage d'amplitude lineaire ont ete effectues. Les resultats ont montre que les proprietes analysees du mastic d'asphalte dependent du type de dosage administre et du type d'essai. En outre, les mastics HL, PC, BFS et LDSS ont montre une meilleure performance par rapport au mastic LS de controle. [Traduit par la Redaction] Mots-cles: mastic d'asphalte, produit de remplissage, dosage du poids et du volume, proprietes rheologiques., Introduction Asphalt mastic is a composite material consisting of asphalt binder, fillers smaller than 75 [micro]m (Little and Petersen 2005; Zulkati et al. 2012; Kuity et al. 2014; Davis and [...]

To study the deformation and failure mechanism of hard rocks, true triaxial compression tests were conducted on four types of hard rocks to obtain the complete stress-strain curves and failure modes. Under true triaxial compression conditions, the shapes of the complete stress-strain curves can be divided into three types: elastic-brittle (EB), elastic-plastic-brittle (EPB), and elastic-plastic-ductile (EPD) types. According to the different post-peak deformation behaviours, the stress-strain curves of EPB type can be subdivided into three sub-categories: post-peak instantaneous brittle (EPB-I), postpeak multi-stage brittle (EPB-M), and post-peak delayed brittle (EPB-D). The stress-strain curves change from EPD to EPB-D, EPB-M, EPB-I, and finally EB with increasing differential stress ([[sigma].sub.2] - [[sigma].sub.3]). The deformation characteristics are dependent on intermediate principal stress [[sigma].sub.2], minimum principal stress [[sigma].sub.3], mineral compositions, and mineral textures of rock samples. An increase in [[sigma].sub.3] leads to an increased ductility, while an increase in [[sigma].sub.2] leads to an increased brittleness. Moreover, rocks with regular mineral textures and low mineral hardness are more prone to ductility. When the deformation curve is transformed from EPD to EPB and then to EB, the tensile crack gradually predominates, and the macroscopic failure angle gradually becomes steeper. Key words: differential stress, mineral properties, tensile crack, deformation behaviour, failure modes. Afin d'etudier le mecanisme de deformation et de rupture des roches dures, de veritables essais de compression triaxiale ont ete realises sur quatre types de roches dures pour obtenir les courbes completes de contrainte-deformation et les modes de rupture. Dans des conditions de compression triaxiale reelle, les formes des courbes completes de contrainte-deformation peuvent etre divisees en trois types : elastique-fragile (EB), elastique-plastique-fracture (EPB) et elastique-plastique-ductile (EPD). En fonction des differents comportements de deformation post-crete, les courbes de contrainte-deformation du type EPB peuvent etre subdivisees en trois sous-categories : cassant instantane post-crete (EPB-I), cassant multi-etapes post-crete (EPB-M) et cassant retarde post-crete (EPB-D). Les courbes de contrainte-deformation changent de EPD a EPB-D, EPB-M, EPB-I, et finalement EB avec une contrainte differentielle croissante ([[sigma].sub.2] - [[sigma].sub.3]). Les caracteristiques de deformation dependent de la contrainte principale intermediate [[sigma].sub.2], de la contrainte principale minimum [[sigma].sub.3], des compositions minerales et des textures minerales des echantillons de roche. Une augmentation de [[sigma].sub.3] conduit a une ductilite accrue, tandis qu'une augmentation de [[sigma].sub.2] conduit a une fragilite accrue. De plus, les roches de texture minerale reguliere et de faible durete minerale sont plus sujettes a la ductilite. Lorsque la courbe de deformation est transformee d'EPD en EPB puis en EB, la fissure de traction predomine progressivement, et l'angle de rupture macroscopique devient progressivement plus prononce. [Traduit par la Redaction] Mots-cles: stress differentiel, proprietes minerales, fissure de traction, comportement de deformation, modes de defaillance., Introduction The stability of excavations in rock engineering (including deep tunnels and underground chambers) is of interest. As the depth of underground engineering operations gradually increases, rock masses are frequently [...]

The innovative carbonation technique based on reactive MgO and C[O.sub.2] has been identified as an environmentally friendly and efficient method in the improvement of weak soils. Previous laboratory studies have indicated that carbonated MgO-admixed soils had significant improvement in mechanical properties. However, there are to date limited investigations on the soft-soil field application of this technique. In this study, a field trial was conducted to ascertain the feasibility of the MgO mass carbonation technique in improving shallow soft-soil subgrades. A series of field tests, including temperature, dynamic cone penetrometer, and light-weight deflectometer tests, were undertaken. The results indicated that compared with uncarbonated soil layers, there was two to three times increase in dynamic resilient moduli and soil resistances of carbonated MgO-admixed soils. The outcomes of this field investigation will contribute to the utilization of the combined stabilizer of MgO and C[O.sub.2] and the mass carbonation technology in subgrade improvement. Key words: mass carbonation, reactive magnesia, soft soil, field investigation, engineering properties. La technique innovante de carbonatation basee sur le MgO et le C[O.sub.2] reactifs a ete identifiee comme une methode efficace et respectueuse de l'environnement pour l'amelioration des sols fragiles. Des etudes anterieures en laboratoire ont indique que les sols carbonates additionnes de MgO presentaient une amelioration significative de leurs proprietes mecaniques. Toutefois, il existe a ce jour peu d'etudes sur l'application de cette technique sur le terrain en sol mou. Dans cette etude, un essai sur le terrain a ete mene pour verifier la faisabilite de la technique de carbonatation de masse du MgO dans l'amelioration des sous-sols mous peu profonds. Une serie d'essais sur le terrain, comprenant des tests de temperature, de penetrometre dynamique a cone et de deflectometre leger, a ete entreprise. Les resultats ont indique que, par rapport aux couches de sol non carbonatees, les modules de resilience dynamique et les resistances du sol des sols carbonates additionnes de MgO etaient deux a trois fois plus eleves. Les resultats de cette enquete sur le terrain contribueront a l'utilisation du stabilisateur combine de MgO et de C[O.sub.2] et de la technologie de carbonatation de masse dans l'amelioration des couches de fondation. Mots-cles: carbonatation de masse, magnesie reactive, sol meuble, etude de terrain, proprietes techniques., Introduction Soft soils, prevalent in floodplains, deltas, and coastal areas such as East China regions, are usually discouraged from direct use in engineering practices due to low strength and permeability [...]

Reflection cracking is a critical issue in asphalt overlay pavement. Temperature variation and traffic loading are the main fracture modes acting on the material. In this paper, a multi-modal overlay tester is proposed for the evaluation of the reflection cracking resistance of an asphalt mixture, an approach that simulates three loading modes on asphalt specimens. A fine dense-grade hot mix asphalt is used as the test specimen and subjected to different loading conditions such as single Mode I, II, and III loading simulations and combined I+II and I+II+III loading simulations. Results show coefficients of variation (CVs) of 2.5%, 10.3%, and 7.4% for the Mode I, II, and III loading simulations, respectively. Furthermore, the [beta] coefficient, with a CVof 7%, is used to represent the crack resistance of the asphalt mixture. Finally, the crack propagation occurs rapidly when subjected to tension and lateral displacement prior to repeated traffic loading simulations. Key words: fatigue test, mixed loading mode, reflection cracking, asphalt overlay tester. La fissuration par reflexion est un probleme critique pour les chaussees asphaltees. La variation de temperature et la charge de roulage sont les principaux modes de rupture agissant sur le materiau. Dans le present document, un appareil d'essai de revetement multimodal est propose pour l'evaluation de la resistance a la fissuration par reflexion d'un melange d'asphalte, une approche qui simule trois modes de chargement sur des echantillons d'asphalte. Un asphalte melange a chaud a base d'agregat a haute densite est utilise comme echantillon d'essai et soumis a differentes conditions de chargement, comme des simulations de chargement en mode I, II et III simples et des simulations de chargement combinees I+II et I+II+III. Les resultats montrent des coefficients de variation (CV) de 2,5, 10,3 et 7,4 % pour les simulations de chargement des modes I, II et III, respectivement. De plus, le coefficient [beta], avec un CV de 7 %, est utilise pour representer la resistance a la fissuration du melange d'asphalte. Enfin, la propagation des fissures se produit rapidement lorsqu'elles sont soumises a une traction et a un deplacement lateral avant les simulations repetees de charges de roulage. [Traduit par la Redaction] Mots-cles : essai de fatigue, mode de chargement mixte, fissuration par reflexion, appareil d'essai de revetement bitumineux., Introduction Reflection cracking is a major problem that needs to be overcome in asphalt overlays on Portland cement concrete (PCC) pavement. Accordingly, the design of an asphalt overlay requires accurate [...]

During large earthquake events where bending moments within soil cements are induced, the tensile strength of cemented soil may govern the deformational behavior of improved ground. Several studies have been conducted to assess the tensile strength of artificially cemented sands that use Portland cement or gypsum; however, the tensile strength of microbially induced carbonate precipitation (MICP)-treated sands with various particle sizes measured through direct tension tests has not been evaluated. MICP is a biomediated improvement technique that binds soil particles through carbonate precipitation. In this study, the tensile strength of nine specimens were measured by conducting direct tension tests. Three types of sand (coarse, medium, and fine) were cemented to reach a heavy level of cementation (e.g., shear wave velocity of ~900 m/s or higher). The results show that the tensile strength varies between 210 and 710 kPa depending on sand type and mass of carbonate. Unconfined compressive strength (UCS) tests were performed for each sand type to assess the ratio between tensile strength and UCS in MICP-treated sands. Scanning electron microscopy (SEM) images and surface energy measurements were used to determine the predominant failure mode at particle contacts under tensile loading condition. Key words: bio-cementation, MICP, tensile strength, unconfined compressive strength (UCS). Pendant les tremblements de terre de grande ampleur ou lors de moments de flexion dans de ciments de sol induits, la resistance a la traction du sol cimente peut regir le comportement de deformation d'un sol ameliore. Plusieurs etudes ont ete realisees pour evaluer la resistance a la traction des sables cimentes artificiellement utilisant du ciment Portland ou du gypse; cependant, la resistance a la traction de sables traites par precipitation carbonatee induite par des microorganismes (MICP) dont la taille de particules varie, mesuree par essai de tension directe n'a pas ete evaluee. Le MICP est une technique d'amelioration biomediee reliant les particules du sol par precipitation carbonatee. Dans cette etude, la resistance a la traction de neuf eprouvettes a ete mesuree par des essais de traction directe. Trois types de sable (grossier, moyen et fin) ont ete cimentes afin d'atteindre un niveau eleve de scellement (p. ex. vitesse de l'onde de cisaillement de ~900 m/s ou plus). Les resultats demontrent que la resistance a la traction varie entre 210 et 710 kPa selon le type de sable et selon la masse de carbonate. Des essais de resistance a la compression sans confinement ont ete realises pour chaque type de sable dans le but d'evaluer le rapport entre la resistance a la traction et la resistance a la compression sans confinement dans les sables traites au MICP. Des images la microscopie electronique a balayage (MEB) et des mesures de l'energie de surface ont ete utilisees pour determiner le mode de defaillance predominant aux contacts de particules soumis a la charge de traction. [Traduit par la Redaction] Mots-cles: biocimentation, MICP, resistance a la traction, resistance non confinee a la compression (UCS)., 1. Introduction Tensile strength is an important parameter that governs the behavior of cemented sands in some special cases. As an example, Namikawa et al. (2007) evaluated the dynamic behavior [...]

The location near the touchdown zone of a steel catenary riser at the seabed is a primary 'hot spot' for fatigue assessment, with seabed stiffness having a major influence on the predicted fatigue life. This paper presents the results of laboratory model tests in the lateral direction with the motivation to appropriately capture the fundamental mechanism of soil interaction with the pipeline or riser in the lateral direction. The objectives of this study are to evaluate (i) the fundamental mechanism of soil interaction with the pipeline or riser in the lateral direction subjected to monotonic and cyclic loading, (ii) the evolution of lateral resistance with different (small to large) displacement amplitudes, (iii) the degradation of lateral resistance while increasing the number of cycles, and (iv) the recovery of the soil strength with time. The primary findings from the tests are that (i) the lateral resistance on the riser-pipeline drops sharply after trench formation, (ii) the lateral resistance across the trench approaches zero and reaches a steady state at a large number of cycles, (iii) the shape of trenches depends on the lateral displacement amplitude and the initial penetration depth, and (iv) some regain in strength occurs after a period for consolidation. Key words: steel catenary riser, soil interaction with pipeline-riser, degradation of lateral resistance, small and large lateral cyclic loading displacement, trench formation, pipeline-riser fatigue assessment. L'emplacement pres de la zone de toucher des roues d'un elevateur catenaire en acier sur le fond marin est un<> principal pour revaluation de la fatigue, la rigidite du fond marin ayant une influence majeure sur la duree de vie prevue. Cet article presente les resultats d'essais en laboratoire sur des modeles de laboratoire dans le sens lateral avec la motivation de bien saisir le mecanisme fondamental de l'interaction pipeline ou elevateur avec sol dans le sens lateral. L'objectif de cette etude est d'evaluer (i) le mecanisme fondamental de l'interaction pipeline ou ascenseur avec sol dans le sens lateral soumis a une charge monotone et cyclique, (ii) revolution de la resistance laterale avec des amplitudes de deplacement differentes (petites a grandes), (iii) la degradation de la resistance laterale tout en augmentant le nombre de cycles, et (iv) la recuperation de la resistance du sol avec le temps. Les principaux resultats des tests sont les suivants: (i) la resistance laterale sur la riser/pipeline diminue fortement apres la formation de la tranchee, (ii) la resistance laterale a travers la tranchee s'approche de zero et atteint un etat stable a un grand nombre de cycles, (iii) la forme des tranchees depend de l'amplitude du deplacement lateral et de la profondeur de penetration initiale, et (iv) un certain regain de vigueur se produit apres une periode de consolidation. [Traduit par la Redaction] Mots-cles: elevateur catenaire en acier, interaction entre le pipeline et le sol, degradation de la resistance laterale, deplacement de charges cycliques laterales petites et grandes, formation de tranchees, evaluation de la fatigue du pipeline et de l'elevateur., Introduction Steel catenary risers (Fig. 1a) that connect floating platforms with seabed facilities are routinely used in offshore oil and gas developments. One of the key design challenges of SCRs [...]

This study compiles a broad database containing 312 measured maximum soil nail loads under operational conditions. The database is used to re-assess the prediction accuracies of the default Federal Highway Administration (FHWA) nail load model and its modified version previously reported in the literature. Predictions using the default and modified FHWA models are found to be highly dispersive. Moreover, the prediction accuracy is statistically dependent on the magnitudes of the predicted nail load and several model input parameters. The modified FHWA model is then recalibrated by introducing extra empirical terms to account for the influences of wall geometry, nail design configuration, and soil shear strength parameters on the evolvement of nail loads. The recalibrated FHWA model is demonstrated to have much better prediction accuracy compared to the default and modified models. Next, an artificial neural network (ANN) model is developed for mapping soil nail loads, which is shown to be the most advantageous one as it is accurate on average and the dispersion in prediction is low. The abovementioned dependency issue is also not present in the ANN model. The practical value of the ANN model is highlighted by applying it to reliability-based designs of soil nails against internal limit states. Key words: soil nail wall, maximum nail load, artificial neural network, model uncertainty, reliability-based design. Cette etude compile une vaste base de donnees contenant 312 charges maximales mesurees de clous de sol dans des conditions operationnelles. La base de donnees est utilisee pour reevaluer l'exactitude des previsions du modele de charge de clouage par defaut de la Federal Highway Administration (FHWA) et de sa version modifiee precedemment rapportee dans la litterature. Les predictions utilisant le modele par defaut et le modele modifie de la FHWA s'averent tres dispersives. De plus, la precision de la prediction depend statistiquement de l'amplitude de la charge prevue des clous et de plusieurs parametres d'entree du modele. Le modele modifie de la FHWA est ensuite recalibre en introduisant des termes empiriques supplementaires pour tenir compte des influences de la geometrie des Mursla configuration de la conception des clous et les parametres de resistance au cisaillement du sol sur revolution de la charge des clous. Il a ete demontre que le modele de la FHWA recalibre a une bien meilleure precision de prediction que le modele par defaut et le modele modifie. Ensuite, un modele de reseau neuronal artificiel (ANN) est developpe pour cartographier les charges de clous du sol, qui s'avere etre la plus avantageuse car elle est precise en moyenne et la dispersion dans la prediction est faible. Le probleme de dependance susmentionne n'est pas non plus present dans le modele ANN. La valeur pratique du modele ANN est mise en evidence en appliquant aux conceptions fondees sur la fiabilite des clous de sol aux etats limites internes. [Traduit par la Redaction] Mots-cles : paroi des ongles du sol, charge maximale des ongles, reseau neuronal artificiel, incertitude du modele, conception basee sur la fiabilite., 1. Introduction As one of the most cost-effective, time-efficient reinforcing techniques, soil nailing has been widely used to stabilize cut slopes, pit excavations, railway embankments, shorelines, etc. (GEO 2008; Griggs [...]

This paper presents the finite-element (FE) block shear failure (BSF) deformation-to-fracture analysis. FE analysis reveals the following: BSF begins with bolt-9bolt hole contact point compressive yielding and not the tensile or shear yielding reported in the literature. BSF does not result from the combination of the gauge tensile plane tensile deformation and the shear plane pure shear deformation alone as reported in the literature and codes. BSF results from compressive deformation of the bolt - bolt hole contact points, tensile deformation of bolt hole portions not in contact with the bolts, gauge tensile plane and edge distance tensile plane deformations in combination with pure shear deformation and a combined shear and tensile bending deformation of the portions of the shear planes near to and remote from the bolt - bolt hole contact points, respectively. This study provides a better understanding of the BSF mechanism, BSF total load-bearing areas, and various resistances to deformation that contribute to the block shear capacity. Key words: block shear failure, finite element, bolt hole elongation, bolt hole compressive deformation, pure shear deformation, tensile bending deformation, shear lip. Cet article presente l'analyse de la deformation jusqu'a la rupture par elements finis (EF) de la rupture par cisaillement de bloc (RCB). L'analyse par EF revele ce qui suit: la RCB commence par la deformation en compression des points de contact boulon - trou de boulon et non par des deformations de traction ou de cisaillement rapportees dans la litterature. Le BSF ne decoule pas de la combinaison de la deformation en traction du plan d'epaisseur - deformation en traction et de seule la deformation pure de cisaillement des plans de cisaillement rapportee dans la litterature et les codes. La RCB provient d'une combinaison de la deformation en compression des points de contact boulon - trou de boulon, de la deformation en traction des parties de trou de boulon qui ne sont pas en contact avec les boulons, deformation du plan de traction manometrique et deformation du plan de traction de la distance du bord avec une deformation de cisaillement pure et une deformation combinee de cisaillement et de flexion de traction des parties des plans de cisaillement situees a proximite et a distance des points de contact boulon - trou de boulon, respectivement. Cette etude permet de mieux comprendre le mecanisme de la RCB, les surfaces portantes totales de la RCB et les diverses resistances a la deformation qui contribuent a la capacite de cisaillement des blocs. [Traduit par la Redaction] Mots-cles: rupture par cisaillement de bloc, element fini, allongement de trou de boulon, deformation par compression de trou de boulon, deformation par cisaillement pur, deformation par flexion en traction, levre de cisaillement., 1. Introduction The fracture of steel-structure connections has been observed in service. Typical examples are the fracture of connections in steel-framed buildings during the Northridge and Kobe earthquakes (Kavide and [...]

Soil reinforcement has rapidly become one of the most common soil improvement techniques used in geotechnical engineering. Understanding the behavior of a geogrid under pullout loading is essential for the analysis and design of reinforced soil systems. The overall behavior of reinforced soils is generally dependent on the properties of the geogrid material, the backfill soil, and the interface condition. Modeling the three-dimensional aspects of soil-geogrid interaction under pullout loading condition is numerically challenging and requires special consideration of the different modes of resistance that contribute to the pullout capacity of the geogrid reinforcement. This study describes the results of a three-dimensional finite-element analysis that has been developed to investigate the behavior of a biaxial geogrid embedded in granular backfill material and subjected to pullout loading. The modeling approach considers the noncontinuous nature of the geogrid geometry and the elastoplastic response of the geogrid material. Model validation is performed by simulating laboratory-size pullout test and comparing the experimental data with the analytical as well as numerically calculated results. The detailed behavior of the geogrid and the surrounding backfill is investigated using the proposed numerical approach. Conclusions are made to highlight the suitability of this technique for analyzing similar soil-structure interaction problems. Key words: geosynthetics, biaxial geogrid, pullout test, soil-geogrid interaction, frictional resistance, bearing resistance, nonlinear contact. Le renforcement des sols est rapidement devenu l'une des techniques d'amelioration des sols les plus couramment utilisees en genie geotechnique. La comprehension du comportement de la geogrille sous charge d'arrachement est essentielle pour l'analyse et la conception des systemes de sols renforces. Le comportement general des sols renforces depend generalement des proprietes du materiau de la geogrille, du sol de remblai et de l'etat de l'interface. La modelisation des aspects tridimensionnels de l'interaction sol-geogrille dans des conditions de charge d'arrachement est un defi numerique et necessite une attention particuliere aux differents modes de resistance qui contribuent a la capacite d'arrachement de l'armature geogrille. Cette etude decrit les resultats d'une analyse tridimensionnelle par elements finis qui a ete mise au point pour etudier le comportement d'une geogrille biaxiale noyee dans un materiau de remblai granulaire et soumise a une charge par arrachement. L'approche de modelisation tient compte de la nature non continue de la geometrie de la geogrille et de la reponse elastoplastique du materiau de la geogrille. La validation du modele s'effectue en simulant un essai d'arrachement de la taille d'un laboratoire et en comparant les donnees experimentales avec les resultats analytiques et les resultats calcules numeriquement. Le comportement detaille de la geogrille et du remblai environnant est etudie a l'aide de l'approche numerique proposee. Des conclusions sont tirees pour souligner la pertinence de cette technique pour analyser des problemes d'interaction sol-structure similaires. [Traduit par la Redaction] Mots-cles: geosynthetiques, geogrille biaxiale, test d'arrachement, interaction sol-geogrille, resistance au frottement, resistance portante, contact non lineaire., Introduction Geosynthetic reinforcements are used in various geotechnical engineering applications, including reinforced earth fills, retaining walls, embankments, paved roads, and foundations. The use of geosynthetics is known to improve soil [...]

A numerical study using a three-dimensional finite element model was conducted to investigate the arching behaviour and strength of concrete masonry infills bounded by reinforced concrete frames subjected to out-of-plane loading. Physical specimens were concurrently tested to provide results for validation of the model as well as evidence of directional characteristics of arching behaviour of masonry infills. A subsequent parametric study using the model included a wide range of infilled frame geometric properties. The results showed in detail the difference in one-way and two-way arching in terms of both strength and failure mechanism, and the contributing factors to this difference. Evaluation of the two main design equations for out-of-plane strength of masonry infills led to proposal of modifications to provide a more rational consideration of directional behaviour of concrete masonry infills. A comparison study using the available test results showed a marked improvement of strength prediction based on the proposed modification. Key words: concrete masonry infills, reinforced concrete frames, out-of-plane, strength, finite element, arching action, nonlinear analysis. Une etude numerique utilisant un modele a elements finis tridimensionnel a ete effectuee pour etudier le comportement de voute et la resistance des remplissages de maconnerie de beton delimites par des charpentes en beton arme soumis a un chargement hors plan. Des specimens physiques ont ete mis a l'essai simultanement pour fournir des resultats de validation du modele ainsi que des preuves des caracteristiques directionnelles du comportement de voute des remplissages de maconnerie. Une etude parametrique subsequente au moyen du modele comprenait une vaste gamme de proprietes geometriques de la charpente avec remplissage de maconnerie. Les resultats ont montre en detail la difference entre les effets de voute unidirectionnels et bidirectionnels au niveau de la resistance et du mecanisme de defaillance, ainsi que les facteurs qui ont contribue a cette difference. L'evaluation des deux equations de conception principales pour la resistance hors plan des remplissages de maconnerie a mene a la proposition de modifications afin d'apporter une consideration plus rationnelle du comportement directionnel des remplissages de maconnerie de beton. Une etude comparative utilisant les resultats d'essais disponibles a montre une amelioration marquee de la prediction de la resistance reposant sur la modification proposee. [Traduit par la Redaction] Mots-cles : remplissage de maconnerie de beton, charpentes en beton arme, hors plan, resistance, element fini, action de voutement, analyse non lineaire., Introduction Masonry walls, when constructed within either a reinforced concrete (RC) or steel frame, are often referred to as masonry infills. It is well recognized that the behaviour and failure [...]

An experimental investigation of the withdrawal resistance of self-tapping screws (STS) inserted parallel-to-grain in Douglas fir and eastern white pine, dry (7% - 6% MC) and wet (28% MC), is conducted. Withdrawal tests with 10 mm screws showed that at an embedment length of 240 mm in dry Douglas fir, 280 mm in wet Douglas fir, and 320 mm in dry eastern white pine, the screws consistently failed by yielding in tension. Withdrawal tests of 12 mm screws and a constant embedment length of 280 mm showed that a longer embedment length is needed compared to the 10 mm screws to ensure tensile screw failure consistently occurs. For both the 10 mm and 12 mm screws, the withdrawal resistance was lower for the wet wood as compared to dry. The CSA O86 equation for lag screws significantly under-predicts the withdrawal resistance of STSs inserted parallel-tograin. Key words: timber connections, self-tapping screws, withdrawal tests, parallel-to-grain, embedment length, Douglas fir, eastern white pine, CSA O86. Une etude experimentale de la resistance au retrait des vis autotaraudeuses (VAT) inserees parallelement au grain dans le sapin Douglas et le pin blanc, sec (7-6 % teneur en humidite (TH)) et humide (28 % TH), est menee. Les essais de retrait avec des vis de 10 mm ont montre qu'a une longueur d'enfoncement de 240 mm dans du Douglas sec, de 280 mm dans du Douglas humide et de 320 mm dans du pin blanc sec, les vis se sont constamment rompues en cedant en traction. Les essais de retrait des vis de 12 mm et d'une longueur d'enfoncement constante de 280 mm ont montre qu'il fallait une longueur d'enfoncement plus longue que celle des vis de 10 mm pour assurer une rupture constante de la vis en traction. Pour les vis de 10 et 12 mm, la resistance au retrait etait inferieure dans le bois humide comparativement au bois sec. L'equation O86 de la CSA pour les tire-fonds sous-estime considerablement la resistance au retrait des VAT inserees parallelement au grain. [Traduit par la Redaction] Mots-cles: assembleur, vis autotaraudeuses, essais de retrait, parallele au grain, longueur d'enfoncement, sapin de Douglas, pin blanc, CSA O86., Introduction Innovations in engineered wood products, timber fasteners, and pre-engineered timber connection systems are contributing to new large-scale structures using timber as the primary structural material (Asdrubali et al. 2017; [...]

This study presents a field-scale simulation of the Hongshiyan landslide in China. It uses an advanced numerical approach (material point method (MPM)) and a constitutive model (the Drucker- Prager model + [mu](I) rheological relation) for the three-dimensional (3D) simulation. The performance of the developed MPM model is validated with laboratory-scale experimental data on granular collapse before being applied to field-scale analyses. ArcGIS data are used to create a 3D MPM model of the soil body with complicated geometry. Although the developed model can describe the multiple phases of granular flow, it focuses on the runout behavior of the landslide in this work. The landslide is assumed to have occurred suddenly due to an earthquake, and global sudden failure rather than progressive failure is modeled. The MPM simulation results match reasonably well with the measured post-earthquake topography (e.g., deposit height of about 120 m and stretch length of about 900 m in the river) and landslide duration of about 1 min. The velocity of the sliding mass increases rapidly during flow, especially in the first 20 s. The velocity profiles along the depth direction at different locations of the sliding body exhibit an exponential distribution similar to that of a Bagnold-type profile, indicating that the sliding body is fully mobilized. The rate-dependent dissipation parameter j3 used in the model significantly influences the runout behavior (e.g., flow speed, velocity distribution, and deposit shape). Key words: landslide, material point method, ArcGIS, rheological relation. Cette etude presente une simulation a l'echelle du terrain du glissement de terrain de Hongshiyan en Chine. Il utilise une approche numerique avancee (methode du point materiel (MPM)) et un modele constitutif (modele Drucker-Prager + [mu](I) relation rheologique) pour la simulation tridimensionelle (3D). Les performances du modele MPM developpe sont validees a l'aide de donnees experimentales a l'echelle du laboratoire sur le collapsus granulaire avant d'etre appliquees a des analyses a l'echelle du champ. Les donnees ArcGIS sont utilisees pour creer un modele MPM 3D du corps du sol avec une geometrie complexe. Bien que le modele developpe puisse decrire les multiples phases d'un ecoulement granulaire, il se concentre sur le comportement a la fin du glissement de terrain dans ce travail. Le glissement de terrain est suppose s'etre produit soudainement a cause d'un tremblement de terre, et un echec mondial soudain plutot qu'un echec progressif est modelise. Les resultats de la simulation MPM correspondent raisonnablement bien a la topographie mesuree apres le seisme (par exemple, hauteur de depot d'environ 120 m et longueur d'etirement d'environ 900 m dans la riviere) et duree de glissement de terrain d'environ 1 min. La vitesse de la masse glissante augmente rapidement lors de l'ecoulement, en particulier dans les 20 premieres secondes. Les profils de vitesse dans la direction de la profondeur a differents endroits du corps glissant presentent une distribution exponentielle similaire a celle d'un profil de type Bagnold, indiquant que le corps glissant est entierement mobilise. Le parametre de dissipation dependant de la vitesse j3 utilisee dans le modele influe de maniere significative sur le comportement a la sortie (par exemple, la vitesse d'ecoulement, la distribution de la vitesse et la forme du depot). [Traduit par la Redaction] Mots-cles: glissement de terrain, methode du point materiel, ArcGIS, relation rheologique., Introduction On 3 August 2014, a Ms6.5 earthquake with a focal depth of 12 km shocked the margin of the Tibetan plateau in Ludian County, Yunnan Province, China (27.10[degrees]N, 103.33[degrees]E) [...]

In deep underground rock engineering projects, rocks are under static pre-load and they may further experience dynamic load due to earthquakes or production blasts. It is thus desirable to consider dynamic failure of rocks subjected to static pre-load. Besides, bending load is commonly encountered near underground openings. Therefore, this study considers the effect of the pre-load on the dynamic bending strength of Laurentian granite (LG). Using a modified split Hopkinson pressure bar system, the semi-circular bend (SCB) method is applied to carry out the bending tests. Five groups of SCB specimens are tested under different pre-loads and loading rates. The results show that under a given pre-load, the flexural tensile strength of LG increases with the loading rate, and decreases with the static pre-load at a given loading rate. The total flexural tensile strength is roughly independent of the pre-load. An empirical equation is used to represent the effects of the loading rate and the pre-load force on the dynamic flexural tensile strength. Furthermore, the flexural tensile strengths measured from SCB tests have higher values than the tensile strengths measured using the Brazilian disc method for the same rock. A nonlocal failure theory is utilized to quantitatively interpret this discrepancy.Key words: flexural tensile strength, pre-load, split Hopkinson pressure bar (SHPB), semi-circular bend (SCB), nonlocal theory.Dans les projets d'ingenierie en profondeur des roches souterraines, les roches sont soumises a une precharge statique et peuvent subir une charge dynamique due a des seismes ou a des explosions de production. Il est donc souhaitable de considerer la rupture dynamique des roches soumises a une precharge statique. En outre, la charge de flexion est generalement rencontree pres des ouvertures souterraines. Par consequent, cette etude examine l'effet de la precharge sur la resistance a la flexion dynamique du granite laurentien (<< LG >>). En utilisant un systeme de barres de pression Hopkinson en deux parties, la methode de cintrage semi-circulaire (<>) est appliquee pour effectuer les essais de flexion. Cinq groupes de specimens SCB sont testes sous differentes precharges et taux de chargement. Les resultats montrent que sous une precharge donnee, la resistance a la flexion de LG augmente avec le taux de chargement, et diminue avec la precharge statique a un taux de chargement donne. La resistance totale a la flexion est a peu pres independante de la precharge. Une equation empirique est utilisee pour representer les effets du taux de chargement et de la force de precharge sur la resistance a la flexion dynamique. En outre, les resistances a la flexion mesurees a partir des essais SCB ont des valeurs plus elevees que les resistances a la traction mesurees en utilisant la methode du disque bresilien pour la meme roche. Une theorie de l'echec non local est utilisee pour interpreter quantitativement cette divergence. [Traduit par la Redaction]Mots-cles: resistance a la flexion, precharger,<>,<>, theorie non locale., IntroductionThe operation depth in rock engineering has been increasing and thus it is necessary to consider the effect of the static pre-load due to in situ stresses on the mechanical [...]

Any process that causes a sudden brittle failure of material has the potential to cause earthquake-like seismic events. Cryoseisms represent an underreported class of seismic event due to their (often) small magnitudes. In this paper, we document the phenomenon of some of the largest magnitude lake-associated icequakes ([M.sub.L] 2.0) yet reported. These events occurred nearly simultaneously (within ~2 h) on geographically separate lakes in Alberta, Canada, starting 1 January 2018. We conjecture that these events were caused by the sudden brittle failure of lake ice due to thermal expansion; the effects of the thermal expansion were compounded by the lack of insulating snow cover, high lake water levels, and a rapid onset of atmospheric warming. These factors also contributed to ice-jacking--a repeating process in which thermal contraction produces tensile cracks (leads) in lake ice that are then filled with water that is frozen during the cooling cycle. Thus, any subsequent thermal expansion must be accommodated by new deformation or brittle failure. This ice-jacking process caused creeping ground deformation after the initial brittle failure and again two weeks later following a second warming period. In many cases, the resulting ground deformation was significant enough to cause property damage.Tout processus entrainant une rupture fragile de materiau peut engendrer des evenements sismiques s'apparentant a des tremblements de terre. Les cryoseismes representent une classe sous-signalee d'evenements sismiques en raison de leurs magnitudes (souvent) faibles. Nous documentons le phenomene de certains des tremblements de glace associes a des lacs de plus grande magnitude ([M.sub.L] 2,0) signales a ce jour. Ces evenements se sont produits quasi simultanement (sur une periode d'environ 2 h) dans des lacs separes dans l'espace en Alberta (Canada), a compter du 1er janvier 2018. Nous postulons que ces evenements etaient causes par la rupture fragile soudaine de la glace de lac en raison de l'expansion thermique; les effets de l'expansion thermiques ont ete amplifies par l'absence d'une couverture de neige isolante, les niveaux eleves des lacs et le rechauffement atmospherique rapide. Ces facteurs ont egalement contribue au soulevement de la glace, un processus repetitif selon lequel la contraction thermique produit des fractures par traction (chenaux) dans la glace du lac qui se remplissent ensuite d'eau qui gele durant le cycle de refroidissement, de sorte que toute expansion thermique subsequente doit etre accommodee par une nouvelle deformation ou rupture fragile. Ce processus de soulevement de la glace a cause une deformation par reptation du sol apres la rupture fragile initiale, puis deux semaines plus tard, apres une deuxieme periode de rechauffement. Dans de nombreux cas, la deformation du sol en decoulant etait assez importante pour causer des dommages materiels. [Traduit par la Redaction], IntroductionCryoseisms are a class of seismic event that has garnered increased attention in recent years (Podolskiy and Walter 2016; Aster and Winberry 2017). Understandably, the major part of this attention [...]

The construction of an underground opening leads to changes in the in situ stress regime surrounding the excavation. The opening influences the rock mass owing to the redistribution of the stresses and results in the disturbance of the surrounding ground. At great depths, massive to slightly or moderately fractured rock masses are usually encountered, and under high stresses, they are more likely to behave in abrittle manner during an excavation. While constitutive models have been developed and proposed for the numerical simulation of such excavations using continuum mechanics, this brittle response cannot be simulated accurately enough, since the material behaviour is governed by fracture initiation and propagation. On the contrary, discontinuum approaches are more suitable in such cases. For the purposes of this paper, the brittle behaviour of hard, massive rock masses and the associated spalling failure mechanisms were simulated by employing a finite-discrete element method (FDEM) approach using Irazu software. The generated numerical model was utilized to replicate field conditions based on the observations at the Atomic Energy of Canada Limited (AECL) Underground Research Laboratory (URL) test tunnel located in Pinawa, Manitoba, Canada. The model results are compared with field observation data to explicitly demonstrate the suitability of the method.Key words: excavation damage zone (EDZ), brittle failure, finite-discrete element method (FDEM), tunnelling, spalling.La construction d'une cavite souterraine entrane des changements dans le regime de contrainte in situ entourant l'excavation. La cavite influe sur la masse rocheuse en raison de la redistribution des contraintes et entrane la perturbation du sol environnant. A de grandes profondeurs, des masses rocheuses massives a legerement ou moderement fracturees sont habituellement rencontrees et sous des contraintes elevees, elles sont plus susceptibles de se comporter de maniere fragile au cours d'une excavation. Alors que des modeles constitutifs ont ete developpes et proposes pour la simulation numerique de telles excavations en utilisant la mecanique du continuum, cette reponse fragile ne peut pas etre simulee suffisamment precisement puisque le comportement du materiau est gouverne par l'initiation et la propagation de la fracture. Au contraire, les approches discontinues sont plus appropriees dans de tels cas. Pour les besoins de cet article, le comportement fragile des rocheux durs et massifs ainsi que les mecanismes de rupture de l'ecaillage associes ont ete simules en employant une methode d'elements finis-discrets (FDEM) en utilisant le logiciel Irazu. Le modele numerique genere a ete utilise afin de reproduire les conditions de terrain en fonction des observations effectuees au tunnel d'essai d'Energie atomique du Canada limitee (EACL) Laboratoire souterrain de recherches (URL) situe a Pinawa, au Manitoba, au Canada. Les resultats du modele sont compares aux donnees d'observation sur le terrain afin de demontrer explicitement la pertinence de la methode. [Traduit par la Redaction]Mots-cles : zone des deteriorations d'excavation (EDZ), rupture fragile, methode d'elements finis-discrets (FDEM), tunnellisation, ecaillage., 1. IntroductionThe excavation of underground openings results in changes both in terms of the stress and deformation regimes in the surrounding ground (Addenbrooke and Potts 2001), with the magnitude of [...]

In recent years, rockbursts have occurred frequently during the mining of thick coal seams in China. Use of the top-coal caving or slicing mining method to extract these thick seams may result in distinct geomechanical responses in the strata and, in turn, the pattern of rockburst occurrence around longwall layouts. To establish a thorough understanding of which method (caving or slicing) is better when it comes to preventing rockbursts during the extraction process, a suite of in situ rockburst measurements was conducted. Six typical rockburst-prone collieries were monitored during which a total of 110 rockburst events occurred. Numerical modelling was used to help interpret the observations. Here, we focus on the analysis of these field observations and the numerical simulations employed to develop a conceptual model for rockburst occurrence during caving mining of thick coal seams. We find that caving mining has a certain rockburst-reducing effect in that the method significantly decreases, or even avoids, the occurrence of rockbursts at coalfaces. Moreover, it reduces the scope of the damage likely to be incurred and the severity and frequency of rockbursting. According to the conceptual model, the rockburst- prone area during caving mining is generally the roadway section located a certain distance ahead of the coalface. This distance, which is roughly 10-54 m, is consistent with the rockburst damage observed on site (mostly 10-50 m ahead of the coalface). This rockburst pattern arises because caving mining results in reduced stress concentration, less bottom coal being retained, and wider-ranging fracture zones around the mine openings, especially ahead of the coalface. This makes the rock surrounding the mine openings less likely to accumulate high levels of elastic energy that need releasing and hence it is more difficult to induce rockbursting. Therefore, it is recommended that the top-coal caving method should be the preferred method of extraction when mining coal seams of a certain thickness. Key words: rockburst, thick coal seam, top-coal caving, slicing mining, field investigation, numerical simulation. Au cours des dernieres annees, des eboulements ont frequemment eu lieu pendant l'extraction miniere de couches de charbon epaisses en Chine. L'utilisation de la speleologie de charbon superieur ou la methode d'exploitation par tranchage pour extraire ces couches epaisses peut donner lieu a des reponses distinctes dans les strates geomecaniques et, a son tour, la tendance de l'occurrence d'eboulements autour des emplacements de longue paroi. Afin d'etablir une comprehension approfondie de quelle methode (speleo ou tranchage) est mieux quand il s'agit de prevenir les eboulements au cours du processus d'extraction, une suite de mesures d'eboulements in situ a ete effectuee. Six colliers sujets a des eboulements typiques ont ete suivis dont on a connu un total de 110 evenements d'eboulements. La modelisation numerique est utilisee pour aider a interpreter les observations. Ici, nous nous concentrons sur l'analyse de ces observations sur le terrain et les simulations numeriques utilisees pour developper un modele conceptuel pour l'occurrence d'eboulements pendant l'exploitation miniere de speleologie de charbon epais. Nous constatons que la speleologie miniere a un certain effet sur les eboulements et que la methode diminue considerablement, voire eviter, l'apparition d'eboulements sur le terrain. En outre, il reduit l'etendue des degats qui pourraient eventuellement souffrir et la gravite et la frequence d'eboulements. Selon le modele conceptuel, la zone sujette a des eboulements au cours de l'exploration par speleologie est generalement la section de chaussee situee a une certaine distance sur le terrain. Cette distance, qui est a peu pres 10-54 m, est compatible avec les dommages d'eboulements constates sur le site (plus souvent 10-50 m sur le terrain). Ce modele d'eboulements surgit, car l'exploitation par speleologie aboutit a une concentration de contrainte reduite, et de zones de fracture plus elargies, moins de charbon de fond etant conserve, et une plus large zone de fractures autour des ouvertures de la mine, surtout en avant du terrain. Cela rend la roche entourant les ouvertures de la mine moins susceptibles d'accumuler des niveaux eleves d'energie elastique qui doivent se liberer et c'est pourquoi il est plus difficile a induire des eboulements. Par consequent, il est recommande que la methode speleologie de charbon superieur devrait etre la methode preferee d'extraction lors de l'extraction de couches de charbon d'une certaine epaisseur. [Traduit par la Redaction] Mots-cles: eboulement, epaisse couche de charbon, speleologie de charbon superieur, tranchage minier, enquete sur le terrain, simulation numerique., 1. Introduction Rockbursts are a serious threat to the safe extraction of coal from mines. According to incomplete statistics, more than 700 rockbursts have taken place since 2008 in the [...]

Mechanical root reinforcement is an important parameter to evaluate for stability analysis of rooted slopes. The contribution of roots is however difficult to quantify in situ without time-consuming methods or heavy equipment. Here we report field testing using the newly developed 'corkscrew' method at two different sites with plantings of conifers and blackcurrant. In both sites we found positive correlations between root quantity and root reinforcement in surface layers where many roots were found. Below 125 mm depth, no correlations could be found, probably due to variability in soil stress and gravel content. Roots were shown not only to increase the soil peak strength, but also to add ductility to the soil, i.e., adding strength over much larger displacement ranges. Measured reinforcement, although similar to other experimental studies, was smaller than predicted using existing models. This may be attributed to the distinct difference in shear displacement required to mobilize the strength of rooted soil as compared with fallow soil. At displacements sufficient to mobilize root strength, the soil strength component has reduced from peak to a much smaller residual strength. The corkscrew method proved a promising tool to quantify root reinforcement in field conditions due to its ease of use and short test duration. Key words: root reinforcement, cork screw, vegetation, in situ testing, slope stability. Le renforcement mecanique des racines est un parametre important a evaluer pour l'analyse de la stabilite des pentes enracinees. La contribution des racines est cependant difficile a quantifier in situ sans des methodes qui prennent du temps ou de l'equipement lourd. Nous rapportons ici des essais sur le terrain en utilisant la nouvelle methode, appelee <>, et developpee sur deux sites differents avec des plantes avec des coniferes et du cassis. Dans les deux sites, nous avons trouve des correlations positives entre la quantite de racines et le renforcement des racines dans les couches de surface ou de nombreuses racines ont ete trouvees. Au-dessous de 125 mm de profondeur, aucune correlation n'a pu etre trouvee, probablement en raison de la variabilite du stress du sol et de la teneur de gravier. Les racines ont ete montrees non seulement pour augmenter la resistance maximale du sol, mais aussi pour ajouter de la ductilite au sol, c'est-a-dire ajouter de la resistance sur des plages de deplacement beaucoup plus grandes. Le renforcement mesure, bien que similaire a d'autres etudes experimentales, etait plus petit que prevu, en utilisant des modeles existants. Cela peut etre attribue a la difference nette de deplacement de cisaillement necessaire pour mobiliser la resistance du sol enracine par rapport au sol inexploite. Aux deplacements suffisants pour mobiliser la force des racines, la resistance du sol a ete reduite du maximum a une resistance residuelle beaucoup plus faible. La methode tire-bouchon a demontre un outil prometteur pour quantifier le renforcement des racines dans les conditions du terrain, en raison de sa facilite d'utilisation et de sa courte duree d'essai. [Traduit par la Redaction] Mots-cles: renforcement des racines, tire-bouchons, vegetations, essais in situ, stabilite de pente., 1. Introduction It is well known that roots can positively increase soil strength through reinforcing soil as inclusions inducing a mechanical effect. Part of the soil shear load is taken [...]

Spatial variability in the radius of a jet-grout column is commonly encountered in practice. Although various prediction models for the column radius are available, they have been generally used to predict a nominal radius. The radius variation within a column has been seldom considered. In this study, the intracolumn radius variation was simulated as a lognormal stochastic process. This was done based on the existing prediction models where the column radius can be correlated with the undrained shear strength of in situ soils. A slab consisting of overlapping jet-grout columns was considered. The slab serves as an earth-retaining stabilizing structure in a deep excavation. The effects of radius variation on the mass performance of the slab were examined with the finite-element method. In addition, the positioning errors in jet-grout columns were also investigated. Owing to the random nature of the radius variation, Monte-Carlo simulations were performed to estimate the statistical characteristics of the mass performance of the slab. A strength reduction factor was introduced and tabulated to account for the effects of geometric imperfections in the column radius and column position. With the strength reduction factor, practitioners could quantitatively evaluate the effects of these geometric imperfections in design considerations. Practical recommendations on the column length and column spacing were also proposed. Key words: jet-grouting technique, deep excavation, ground improvement, statistical analysis, stochastic process, finite-element modelling. La variabilite spatiale dans le rayon d'une colonne de coulis a jet est couramment rencontree dans la pratique. Bien que differents modeles de prediction pour le rayon de la colonne soient disponibles, ils etaient generalement utilises pour predire un rayon nominal. La variation du rayon dans une colonne a rarement ete prise en compte. Dans cette etude, la variation du rayon intra colonne a ete simulee comme un processus stochastique log normal. Cela a ete fait sur la base des modeles de prediction existants ou le rayon de la colonne peut etre correle avec la resistance au cisaillement non draine des sols in situ. Une dalle composee de chevauchements de colonnes de coulis a ete consideree. La dalle sert de structure stabilisatrice de retenue de la terre dans une excavation profonde. Les effets de la variation de rayon sur les performances massiques de la dalle ont ete examines avec la methode des elements finis. En outre, les erreurs de positionnement dans les colonnes de coulis a jet ont egalement ete etudiees. En raison de la nature aleatoire de la variation du rayon, les simulations de Monte-Carlo ont ete effectuees pour estimer les caracteristiques statistiques de la performance en masse de la dalle. Un facteur de reduction de la force a ete introduit et compile pour tenir compte des effets des imperfections geometriques dans le rayon de la colonne et la position de la colonne. Avec le facteur de reduction de la force, les praticiens pourraient evaluer quantitativement les effets de ces imperfections geometriques dans les considerations de conception. Des recommandations pratiques sur la longueur de la colonne et l'espacement entre les colonnes ont egalement ete proposees. [Traduit par la Redaction] Mots-cles : technique de jointoiement par jet, excavation profonde, amelioration du sol, analyses statistiques, processus stochastique, modelisation par elements finis., Introduction The jet-grouting technique has been used extensively to facilitate deep excavation and underground construction in a wide spectrum of soils (e.g., Coulter and Martin 2006; Flora et al. 2011; [...]

Rocks containing pre-existing fissures in underground engineering are likely to be subjected to static pre-stress and dynamic loads simultaneously. Understanding the deformation and failure mechanism of fissured rocks under coupled static and dynamic strain rates is beneficial for the stability assessment of rock engineering structures. This study experimentally investigates the mechanical behaviors of fissured specimens under coupled static and dynamic loads with different loading parameters. Our experiments reveal that the coupled static-dynamic strain rates significantly affect the strength, deformation, energy characteristics, and failure mode of fissured specimens. For each dynamic strain rate, the strength and elastic modulus of specimens feature an increase first as the static pre-stress increases up to half of the uniaxial compression strength, and then a decrease. However, for each static pre-stress of coupled loads, the strength and elastic modulus increase noticeably with increasing dynamic strain rate. From the perspective of energy partition, for each static pre-stress, the higher dynamic strain rate induces greater energy dissipation of the specimens during the coupled loading, and more elastic energy is released at the end of loading. Moreover, for each dynamic strain rate, the pre-stress of half uniaxial compression strength induces the highest released elastic energy. Key words: coupled loads, strain rate, mechanical behaviors, energy characteristics, fissured specimen. Les roches contenant des fissures preexistantes dans l'ingenierie souterraine sont susceptibles d'etre soumises simultanement a des contraintes statiques et a des charges dynamiques. La comprehension de la deformation et du mecanisme de defaillance des roches fissurees sous des taux de deformation statique et dynamique couplees est benefique pour l'evaluation de la stabilite des structures d'ingenierie des roches. Cette etude examine experimentalement les comportements mecaniques de specimens fissures sous charges statiques et dynamiques couplees avec differents parametres de chargement. Nos experiences revelent que les taux de deformation statique et dynamique couples affectent de maniere significative la resistance, la deformation, les caracteristiques d'energie et le mode de defaillance des specimens fissures. Pour chaque taux de deformation dynamique, la resistance et le module elastique des echantillons presentent une augmentation d'abord, car le pre-stress statique augmente jusqu'a la moitie de la force de compression uni axiale, puis une diminution. Cependant, pour chaque precontrainte statique des charges couplees, la force et les modules elastiques augmentent de facon evidente avec un taux de deformation dynamique croissante. Du point de vue de la partition d'energie, pour chaque pre-stress statique, le taux de deformation dynamique plus eleve induit une plus grande dissipation d'energie des specimens pendant le chargement couple et une energie plus elastique est publiee a la fin du chargement. De plus, pour chaque taux de deformation dynamique, la precontrainte de la resistance a la compression uni axiale induit l'energie elastique liberee la plus elevee. [Traduit par la Redaction] Mots-cles: charges couplees, taux de deformation, comportement mecanique, caracteristiques energetiques, specimen fissure., Introduction Underground rock engineering works, such as oil exploitation, mining, and geological boring, are likely to be subjected to static pre-stress and dynamic loads simultaneously (Fig. 1). Static pre-stress can [...]

The strength of Milton Queenston shale (MQS) before and after soaking in water and lubricant fluids (LFs) was examined. The investigated LFs (i.e., bentonite and polymer solutions) are utilized in the microtunnelling technique (MTT) to facilitate the installation of tunnel or pipe sections. To investigate the relevant mechanical properties of MQS under different wetting conditions, a series of laboratory tests including Brazilian split, uniaxial compression, and triaxial compression were carried out. These tests were performed on vertically and horizontally cored specimens with respect to the rock bedding. Fresh specimens (i.e., intact) and specimens soaked for 100 days in LFs and in water were examined. The 100 day period was selected, as it may reasonably represent the construction period where some swelling of the Queenston shale can occur. It was revealed that the strength of MQS substantially decreased after soaking. With greater impact in the vertical direction, both water and bentonite solution caused similar decrease in MQS strength of 23%-70%, while polymer solution caused a smaller decrease of 10%-57%. Accordingly, strength envelopes of MQS were established for vertical and horizontal directions before and after soaking. Key words: Queenston shale, peak strength, microtunnelling, lubricant fluids, soaking effects. La force du schiste Queenston Milton (MQS) avant et apres le trempage dans l'eau et de de liquides lubrifiants (LL) a ete examinee. Les LL enquetes (c.-a-d. la bentonite et les solutions polymeres) sont utilises en technique creusement de micro tunnel (MTT) pour faciliter l'installation des sections de tuyaux ou de tunnel. Pour etudier les proprietes mecaniques des sous-differentes conditions de mouillage MQS, une serie de tests de laboratoire y compris le split bresilien, la compression uniaxiale et la compression triaxiale ont ete effectues. Ces essais ont ete effectues sur des echantillons carottes verticalement et horizontalement par rapport a la roche de la literie. Les specimens frais (c.-a-d. intact), et des specimens trempes pendant 100 jours dans les LL et dans l'eau ont ete examines. La periode de 100 jours a ete choisie, car il peut representer raisonnablement la periode de construction ou l'enflure du schiste Queenston peut se produire. Il a ete revele que la resistance de MQS a sensiblement diminue apres le trempage. Avec un plus grand impact dans le sens vertical, a la fois l'eau et la solution de bentonite ont cause une diminution similaire dans les resistances MQS de 23-70 %, alors que la solution de polymere a cause une diminution plus faible de 10-57 %. En consequence, la resistance d'enveloppes MQS a ete etablie pour les sens verticale et horizontale avant et apres le trempage. [Traduit par la Redaction] Mots-cles: schiste Queenston, resistance de pic, creusement de micro tunnel, liquides lubrifiants, effets de trempage., Introduction Microtunnelling is an effective construction technique to install pipelines and tunnels of variable diameters in several types of soil. However, adopting the microtunnelling technique (MTT) to install pipelines and [...]

This paper presents an experimental program to justify the barrier design at the barrier-deck junction when compared to the factored applied transverse vehicular loading specified in the Canadian Highway Bridge Design Code (CHBDC). Compared to the dimensioning and the glass fibre reinforced polymer (GFRP) bar detailing of a recently crash-tested GFRP-reinforced barrier, the adopted barrier configurations in this paper were similar to those specified by Ministry of Transportation of Quebec (MTQ) for TL-5 barrier except that the base of the barrier was 40 mm narrower and the deck slab is of 200 mm thickness, leading to reduction in the GFRP embedment depth into the deck slab. Four full-scale TL-5 barrier specimens were tested to collapse. Correlation between the experimental findings and the factored applied moments from CHBDC equivalent vehicle impact forces resulting from the finite-element modelling of the barrier-deck system was conducted followed by recommendations for use of the proposed design in highway bridges in Quebec. Key words: sand-coated GFRP bars, TL-5 barrier, MTQ barrier, deck-barrier joint, bridge codes and standards, experiments. Dans le cadre de cet article, on presente un programme experimental dans le but de justifier la conception d'une jonction de barriere de pont lorsque comparee a la charge transversale de vehicule appliquee et ponderee comme indique dans le Code canadien sur le calcul des ponts routiers (<< CHBDC >>). Comparees au dimensionnement et a l'exposition en detail de barres en polymere renforce de fibre de verre (<< GFRP >>) d'une barriere ayant recemment subi des essais de collision, les configurations de barriere adoptees dans cette etude etaient semblables a celles definies par le ministere des Transports du Quebec (MTQ) pour la barriere TL-5 sauf que la base de la barriere etait 40 mm plus etroite et la dalle du tablier est d'une epaisseur de 200 mm, menant a la reduction de la profondeur d'encastrement du GFRP dans la dalle du tablier. Quatre specimens de barriere TL-5 a echelle reelle ont ete mis a l'epreuve jusqu'a ecroulement. La correlation entre les resultats experimentaux et les moments appliques ponderes provenant de forces d'impact de vehicule correspondantes a celles du CHBDC resultant de modelisation par elements finis du systeme de barriere de tablier a ete etablie, suivie de recommandations pour l'utilisation de la conception proposee des ponts de route au Quebec. [Traduit par la Redaction] Mots-cles : barres en polymere renforce de fibre de verre (<< GFRP >>) enduites de sable, barriere TL-5, barriere MTQ, joint de barriere de pont, codes et normes de pont, experiences., Introduction Steel reinforcing bars are commonly used in reinforced concrete applications owing to their cost-effectiveness, strength and ductility that are well suited to use in civil engineering structures. However, in [...]

Abstract: An extensive polygonal fault system (PFS) has been recognized in fine-grained Late Cretaceous sediments of the Western Interior Seaway of North America. Polygonal fault systems are pervasive organizations of [...]

Canadian hard rock mines continue to reach deeper deposits, which poses greater challenges to mine safety including rock burst control. Destress blasting techniques have been successfully employed in such underground mines with the aim of preconditioning highly stressed rock mass to mitigate the risk for rock burst occurrence in deep mines. In the present study, the efficiency of destress blasting is examined through a comparison between traditional and alternative numerical modelling approaches. The traditional modelling approach assumes a uniformly distributed blast-induced damage zone extending over the entire drift face, whilst the alternative modelling approach, presented herein, simulates the damage zone for each individual blast hole. In the first part of this paper, a three-dimensional numerical model of a single blast hole is constructed, whereby the extent of blast-induced damage zone is delineated. The latter part of this paper uses the single-hole model results to examine the efficiency of destress blasting as practiced in drift development in deep mines. It is demonstrated through comparison of FLAC3D numerical simulation results that the traditional modelling approach may lead to an overly optimistic indication of destress blasting efficiency when compared with the alternative modelling approach, in which a more precise simulation of the damage zones is applied. Key words: numerical modelling, FLAC3D, rock burst, underground mining. Les mines canadiennes de roches dures continuent d'atteindre les gisements plus profonds, ce qui pose de plus grands defis en matiere de securite, y compris le controle des eclatements de roches dans les mines. Les techniques de tir de relaxation (<< destress blasting >>) ont ete employees avec succes dans des mines souterraines dans le but de preconditionner la masse rocheuse fortement sollicitee pour limiter les risques d'eclatement de roche dans les mines profondes. Dans la presente etude, l'efficacite des tirs de relaxation est examinee par une comparaison entre les approches traditionnelle et alternative de la modelisation numerique. L'approche traditionnelle de la modelisation suppose une zone de dommage uniforme induite par explosion s'etendant sur tout le front de taille de la galerie en direction, tandis que la modelisation alternative, presentee ici, simule la zone de degats pour chaque trou de mine. Dans la premiere partie du present document, un modele numerique en trois dimensions d'un seul trou de mine est construit, auquel l'etendue de la zone de dommages causes par la detonation est delimitee. La derniere partie de cet article utilise les resultats du modele a trou simple afin d'examiner l'efficacite du tir de relaxation tel que pratique pour les galeries en direction dans les mines souterraines. Il est demontre par le biais de la comparaison des resultats par simulation numerique FLAC3D que l'approche traditionnelle de la modelisation peut mener a une indication trop optimiste de l'efficacite du tir de relaxation en comparaison avec la modelisation alternative, a laquelle s'applique une simulation plus precise des zones de dommages. [Traduit par la Redaction] Mots-cles : modelisation numerique, FLAC3D, eclatement de roche, exploitation de mine souterraine., Introduction When tunnels are excavated through competent rock mass under high stress conditions, rock bursts, especially strain bursts, can be a serious issue that poses a high risk to underground [...]

The mechanical behavior of frozen soils is strongly affected by the amount of ice. The amount of ice depends on the temperature and the applied mechanical stresses. The influence of ice content and temperature on the mechanical behavior and the coupling effects on the reverse direction can be mentioned as the main difference between frozen and unfrozen soils. In the light of this difference, an elastoplastic constitutive model for describing the stress-strain behavior of saturated frozen soils is proposed. By dividing the total stress into fluid pressure and solid phase stress, in addition to consideration of the cryogenic suction, the model is formulated within the framework of two-stress state variables. The proposed model is able to represent many of the fundamental features of the behavior of frozen soils, such as ice segregation phenomenon and strength weakening due to pressure melting. In the unfrozen state the model becomes a conventional critical state model. Typical predictions of the model for simulating the characteristic trends of the frozen soil behavior is described qualitatively. Model predictions are also compared with the available test results and reasonable agreement is achieved. Key words: frozen soil, elastoplastic model, cryogenic suction, solid-phase stress. Le comportement mecanique des sols geles est fortement affecte par la quantite de glace. La quantite de glace depend de la temperature et des contraintes mecaniques appliquees. L'influence de la teneur en glace et de la temperature sur le comportement mecanique et les effets de couplage sur le sens inverse peut etre mentionnee comme la principale difference entre les sols geles et non geles. A la lumiere de cette difference, un modele constitutif elastoplastique est propose pour decrire le comportement de contrainte-deformation des sols geles satures est propose. En divisant la contrainte totale en pression du fluide et en contrainte de phase solide, en plus de l'examen de la succion cryogenique, le modele est elabore dans le cadre des variables d'etat de deux contraintes. Le modele propose est en mesure de representer beaucoup de caracteristiques fondamentales du comportement des sols geles comme le phenomene de segregation de glace et l'affaiblissement de la force du fi la pression de fusion. En etat non gele, le modele devient un modele conventionnel de l'etat critique. Les predictions typiques du modele pour simuler l'evolution caracteristique du comportement de sol gele est decrit qualitativement. Les predictions du modele sont egalement comparees avec les resultats des tests disponibles et un accord raisonnable est atteint. [Traduit par la Redaction] Mots-cles : sol gele, modele elastoplastique, succion cryogenique, contrainte de la phase solide., Introduction The constitutive modeling of frozen soils has been closely linked with identifying the relevant stress measurements describing the stress-strain behavior. Total stress-based models have been widely used in the [...]

Production of oil from shallow reservoirs typically involves drilling highly deviated wells through unconsolidated (or poorly lithified) rocks or clays. This paper describes numerical analyses of the deformations and stability of deviated wellbores within a [K.sub.0]-consolidated clay. The analyses consider planar deformations in the plane orthogonal to the wellbore using a quasi three-dimensional (3D) finite element model that represents coupled flow and deformations within the soil mass. Cross-anisotropic mechanical properties of the clay are described by a generalized effective stress model, MIT-E3, with parameters previously calibrated from laboratory thick-walled cylinder tests. The analyses compute the relationship between the drilling mud pressure and wellbore stability associated with either the onset of localized failure mechanisms or large plastic deformations around the cavity. The results show that short-term, undrained stability requires mud pressures in excess of the in situ formation pore pressures for more highly deviated wellbores at inclinations greater than 45°. The analyses examine the mechanisms for further destabilization, due to consolidation within the formation, and how they are affected by drainage conditions at the wellbore wall. The results provide qualitative information for the design and control of drilling operations for deviated wellbores in unconsolidated formations. Key words: numerical analysis, wellbore stability, constitutive model, clay behavior, coupled analysis. La production de petrole dans les reservoirs peu profonds implique generalement le forage de puits tres devies a travers de roches ou argiles non consolidees (ou mal lithifies). Cet article decrit les analyses numeriques des deformations et la stabilite des puits de forage devies dans une argile [K.sub.0]-consolide. Les analyses considerent les deformations planaires dans le plan orthogonal au puits a l'aide d'un modele d'elements finis quasi-tridimensionnel (3D) qui represente le flux couple et les deformations dans la masse de sols. Les proprietes mecaniques anisotropes croisees de l'argile sont decrites par un modele de contrainte effectif, generalise, MIT-E3, avec les parametres prealablement etalonnes a partir d'essais en laboratoire a l'aide d'un appareil triaxial a paroi epaisse. Les analyses calculent la relation entre la pression de boue de forage et la stabilite de puits de forage associee soit avec l'apparition de mecanismes de rupture localisee ou grandes deformations plastiques autour de la cavite. Les resultats montrent qu'a court terme, la stabilite non drainee necessite une pression superieure a la pression in situ de formation de puits de forage pour des puits de forage plus fortement devies a des inclinaisons superieures a 45°. Les analyses examinent les mecanismes de nouvelle destabilisation, en raison de la consolidation au sein de la formation, et comment ils sont affectes par les conditions de drainage a la paroi de puits de forage. Les resultats fournissent des renseignements qualitatifs pour la conception et le controle des operations de forage pour puits devies dans les formations non consolidees. [Traduit par la Redaction] Mots-cles: analyse numerique, stabilite des puits de forage, modele constitutif, comportement de l'argile, analyse couplee., Introduction In the ever expanding search for new sources of oil and gas, the industry is investigating new prospects in very shallow reservoirs (depths less than 1000 m) including deep [...]

In this study, the static lateral behavior of a battered pile group foundation was investigated using three-dimensional finite element (FE) analysis. The FE model was used to simulate the static lateral load test that was performed during the construction of the I-10 Twin Span Bridge over Lake Pontchartrain, La., in which two adjacent bridge piers were pulled against each other. The pier of interest was supported by 24, 1:6 batter, 34 m long piles in a 6 x 4 row configuration. The FE model of the battered pile group was developed in Abaqus and verified using the results from the field test. The model utilized an advanced constitutive model for concrete, which allowed distinct behavior in tension and compression, and introduced damage to the concrete stiffness. The soil domain comprised of several layers in which the constitutive behavior of clay layers was modeled using the anisotropic modified Cam-clay (AMCC) model, and for sands using the elastic perfectly plastic Drucker-Prager (DP) model. FE results showed good agreement with the results of the lateral load test in terms of lateral deformations and bending moments. The results showed that the middle rows carried a larger share of lateral load than the first and the last rows. The pile group resisted a maximum lateral load of 24941 at which the piles were damaged within a 6 m zone from the bottom of the pile cap. The edge piles carried larger internal forces and exhibited more damage compared to the inner piles. The soil resistance profiles showed that soil layering influenced the distribution of resistance between the soil layers. A series of p-y curves were extracted from the FE model, and then used to study the influence of the group effect on the soil resistance. The p-y curves showed that the group effect reduced the soil resistance in all rows, with the lowest resistance in the third row. Finally, the p-multipliers were calculated using the extracted p-y curves, and compared to the reported p-multipliers for vertical pile groups. Key words: lateral behavior, battered pile, pile group, p-y curve, soil-pile interaction, numerical analysis. Dans la presente etude, le comportement lateral statique d'une fondation constituee d'un ensemble de pieux battus a ete etudie l'aide d'une analyse tridimensionnelle basee sur les elements finis (EF). Le modele d'EF a servi simuler un essai de chargement lateral statique qui a ete realise durant la construction du double pont de l'autoroute I-10, qui traverse le lac Pontchartrain (Louisiane) et dont deux piles adjacentes ont ete poussees l'une contre l'autre. La pile etudiee etait supportee par 24 pieux de 34 m de long, battus avec un angle d'inclinaison de 1/6 et disposes en 6 rangees de 4 pieux. Le modele d'EF applique cet ensemble de pieux battus a ete developpe avec le logiciel Abaqus et verifie l'aide des resultats des essais realises sur le terrain. Ce modele s'est appuye sur un modele constitutif elabore s'appliquant au beton, ce qui a permis de simuler des comportements differents en tension et en compression et une deterioration de la rigidite du beton. Le sol etait constitue de plusieurs couches, dans lesquelles le comportement constitutif de couches d'argile a ete modelise l'aide d'un modele Cam-clay modifie anisotrope (CCAM) et, dans le cas de sables, l'aide du modele elastique parfaitement plastique de Drucker-Prager. Les resultats obtenus l'aide du modele d'EF ont semble bien coincider avec ceux des essais de chargement lateral en ce qui concernait les deformations laterales et les moments de flexion. Les resultats ont montre que les rangees du milieu supportaient une portion plus importante de charge laterale que les premieres et dernieres rangees. L'ensemble de pieux a resiste une charge laterale maximale de 2494 t, au-del;i de laquelle les pieux se sont endommages sur une hauteur de 6 m partir de la base de la semelle des pieux. Les pieux situes sur les bords ont subi des forces internes plus importantes et ont davantage de dommages par rapport aux pieux centraux. Les profils de resistance du sol ont montre que la disposition des couches de sol influencait la repartition de la resistance entre ces couches. Une serie de courbes p-y ont ete tracees partir du modele d'EF, puis ont servi etudier l'influence de l'effet de groupe sur la resistance du sol. Les courbes p-y ont montre que l'effet de groupe entrainait une diminution de la resistance du sol dans toutes les rangees de pieux, la resistance la plus faible etant observee dans la troisieme rangee. Enfin, les multiplicateurs p ont ete calcules partir des courbes p-y tracees, puis compares aux multiplicateurs p associes des ensembles de pieux verticaux. [Traduit par la Redaction] Mots-cles: comportement lateral, pieu battu, ensemble de pieux, courbe p-y, interaction sol-pieu, analyse numerique., Introduction The lateral behavior of piles has been well studied in the past decades, with the single pile case mostly investigated. The lateral capacity of a single pile can be [...]

The behaviour of cast-iron cross passages in the London Underground was investigated using three-dimensional finite element models. Unlike the behaviour of a full tunnel ring, the structural integrity of a tunnel cross-passage opening relies on support from adjacent linings. In clayey soils, the opening may deform further as the soil stiffness changes from undrained to drained conditions. Degradation of the circumferential bolts and trackbed may also lead to further tunnel movement. A parametric study was conducted to examine the influence of soil stiffness and structural components (e.g., bolts and lintel) on the structural integrity of a tunnel opening. Results show that a lintel effectively transfers the load above the opening to the adjacent linings, and its distortion affects tunnel deformation significantly. If a lintel is not present, both bolts and friction between tunnel segments provide shear resistance to the lining deformation at the tunnel opening against soil loading. Results are compared with field observations made at a critical cross passage in one of the London Underground tunnels. The findings contributed to identifying the critical deformation mechanisms of cast-iron tunnel cross passages, which can be useful during inspection of such structures. Key words: cast iron lining, cross-passage tunnel, bolt-spring model, lintel, bolts. Le comportement de passages souterrains structure en fonte croisant des tunnels dans le metro de Londres a ete etudie l'aide de modeles d'elements finis tridimensionnels. A la difference de l'anneau qui entoure un tunnel, l'integrite structurale de l'extremite d'un passage souterrain debouchant sur un tunnel depend du soutien assure par les parois adjacentes. Dans les sols argileux, cette extremite peut se deformer lorsque la rigidite du sol varie et que l'on passe de conditions non drainees des conditions drainees. La deterioration des boulons situes la circonference du tunnel et de la plate-forme de la voie de circulation du metro peut egalement occasionner une deformation plus importante du tunnel. On a realise une etude parametrique afin d'analyser les effets de la rigidite du sol et des elements structuraux (p. ex. les boulons et linteaux) sur l'integrite structurale d'une extremite de tunnel. Les resultats montrent qu'un linteau transfere efficacement la charge qui s'exerce dans la partie superieure de l'extremite du tunnel vers les parois adjacentes et que sa distorsion influe beaucoup sur la deformation du tunnel. En l'absence de linteau, les boulons et les frottements qui s'exercent entre les segments de tunnel contribuent la resistance au cisaillement lors de la deformation des parois au niveau de l'extremite du tunnel en presence des charges exercees par le sol. Les resultats sont compares aux observations effectuees sur le terrain, une intersection importante entre un passage souterrain et un tunnel du metro de Londres. Ces observations ont permis d'identifier les mecanismes cles de la deformation de passages souterrains structure en fonte croisant des tunnels, ce qui peut s'averer utile si l'on souhaite inspecter ce type de structure. [Traduit par la Redaction] Mots-cles: paroi en fonte, passage souterrain croisant un tunnel, modele boulon-ressort, linteau, boulons., Introduction The condition of aging underground tunnels presents a significant engineering challenge in many cities (Inokuma and Inano 1996; Mair 2008). The London Underground has a history of more than [...]

During horizontal directional drilling (HDD), the drilling fluid pressure must not surpass the maximum allowable pressure to minimize the risk of hydraulic fracturing; hence, a plan pressure can be used to manage the drilling fluid pressure. This paper addresses the prediction of plan annular pressure using the power law flow model. The annular pressures were predicted using the power law model with rheological parameters determined from a six-speed viscometer with varying shear rate ranges from 3 to 600 RPM for two HDD projects, and the predicted pressures were compared with the measurements. The results indicated that the annular pressure could be properly predicted, and the best prediction was achieved by the shear rate range of 6-100 RPM due to embracing the real shear rate of drilling fluid inside the annulus; this shear rate range is close to the recommendation (3-100 RPM) by American Petroleum Institute Recommended Practice. Key words: horizontal directional drilling, drilling fluid pressure, power law model, rheological parameters, shear rate. Lorsqu'on effectue un forage directionnel horizontal (FDH), il ne faut pas exceder des valeurs limites maximales de pression du fluide de forage afin de minimiser les risques d'effondrement du puits de forage et de fracturation hydraulique, lesquels entrainent une perte de fluide de forage et une augmentation de l'ensemble des risques inherents au chantier de forage. Pour empecher la pression annulaire de detruire le puits de forage et prevenir les risques de fracturation et pour ameliorer la securite des operations de FDH, il est possible de s'appuyer sur des valeurs de pression predites pour assurer le controle de la pression du fluide de forage. Le present article traite de la prediction de la pression annulaire a l'aide d'un modele d'ecoulement base sur une loi de puissance. Les pressions annulaires ont ete predites a l'aide de ce modele et a partir de parametres rheologiques determines au moyen d'un viscosimetre a six vitesses, les taux de cisaillement variant entre 3 et 600 tours/minute dans le cas des deux chantiers de FDH consideres. En outre, les pressions predites ont ete comparees aux valeurs de pression annulaires mesurees en temps reel. Les resultats obtenus montrent que l'utilisation de modele base sur une loi de puissance permet de predire correctement la valeur de la pression annulaire. Par ailleurs, la meilleure prediction a ete effectuee dans un intervalle de taux de cisaillement compris entre 6 et 100 tours/minutes, etant donne que le taux de cisaillement reel du fluide de forage est inclus dans l'anneau. Cet intervalle de taux de cisaillement est proche de celui recommande (3 a 100 tours/minute) par l'American Petroleum Institute Recommended Practice. [Traduit par la Redaction] Mots-cles : forage directionnel horizontal, pression du fluide de forage, modele base sur une loi de puissance, parametres rheologiques, taux de cisaillement., Introduction Horizontal directional drilling (HDD) is a trenchless construction solution to the traditional open-cut method used for utility conduit installation. Over the past four decades, advancements in HDD have made [...]

Calcium carbide residue (CCR) is an industrial by-product, stockpiles of which are rapidly accumulating worldwide. Highway embankment construction has been identified as an avenue to consume huge quantities of CCR as an economical, less energy intensive, and environmentally friendly chemical additive for soil stabilization. Previous studies have investigated the mechanical behavior of soils stabilized by CCR or blends of CCR with other additives; however, interpretation of the macroscale geomechanical behavior of CCR-stabilized soft soils from a systematically microstructural observation and analysis is relatively unknown. This paper presents a multi-scale laboratory investigation on the physical, mechanical, and microstructural properties of CCR-stabilized clayey soils with comparison to quicklime-stabilized soils. Several series of tests were conducted to examine the Atterberg limits, particle-size distribution, compaction characteristics, unconfined compressive strength, California Bearing Ratio, and resilient modulus of the CCR-stabilized clayey soils. The influences of binder content, curing time, and initial compaction state on the physical and mechanical properties of treated soils are interpreted with the aids of physicochemical and microstructural observations including soil pH, soil mineralogy obtained from X-ray diffraction and thermogravimetric analysis, and pore-size distribution obtained from mercury intrusion porosimetry. Soil particle flocculation and agglomeration at the early stage and pozzolanic reactions during the entire curing time, which originate from the finer particle size, greater specific surface area, and higher pH value of CCR, are the controlling mechanisms for the superior mechanical performance of CCR-stabilized soils. The outcomes of this research will contribute to the usage of CCR as a sustainable and alternative stabilizer to quicklime in highway embankment applications. Key words: calcium carbide residue (CCR), multi-scale, pozzolanic reaction, soil stabilization. Les residus de carbure de calcium (RCC) sont des sous-produits industriels et s'accumulent rapidement sous forme de depots en tas dans le monde entier. On a constate que, dans le cadre de la construction des remblais routiers, d'enormes quantites de RCC etaient consommees, car ces derniers constituent un additif chimique peu couteux en energie et ecologique utilise pour stabiliser le sol. De precedentes etudes se sont interessees au comportement mecanique de sols stabilises a l'aide de RCC ou de melanges composes de RCC et d'autres additifs. Cependant, on a jusqu'ici relativement peu etudie, au moyen d'observations et d'analyses microstructurales systematiques, le comportement geomecanique, a l'echelle macroscopique, des sols mous stabilises avec des RCC. Le present article decrit l'etude en laboratoire, a plusieurs echelles, des proprietes physiques, mecaniques et microstructurales de sols argileux stabilises a l'aide de RCC et compare ces dernieres a celles de sols stabilises avec de la chaux vive. On a effectue plusieurs series d'essais afin d'examiner les limites d'Atterberg, la distribution de la taille de particules, les caracteristiques de compactage, la resistance a la compression non confinee, l'indice portant californien et le module de resilience des sols argileux stabilises au moyen de RCC. On a analyse les effets de la teneur en liant, du temps de prise et de l'etat initial de compactage sur les proprietes physiques et mecaniques des sols traites en analysant les caracteristiques physicochimiques et microstructurales, telles que le pH du sol, la composition mineralogique du sol, determinee a l'aide d'analyses diffractometriques et thermogravimetriques, et la distribution de la taille des pores determinee au moyen d'un porosimetre a mercure. La floculation et l'agglomeration precoces des particules du sol et les reactions pouzzolaniques qui ont lieu pendant toute la duree de prise, phenomenes qui s'expliquent tous par la petite taille des particules, leur grande surface specifique et la valeur elevee du pH des residus de carbure de calcium, sont des mecanismes qui contribuent aux excellentes performances mecaniques des sols stabilises au moyen de RCC. Grace aux resultats de la presente etude, les RCC pourront constituer une solution de remplacement durable pour stabiliser la chaux vive lors de la construction de remblais routiers. [Traduit par la Redaction] Mots-cles: residus de carbure de calcium (RCC), a plusieurs echelles, reaction pouzzolanique, stabilisation du sol., Introduction Calcium carbide residue (CCR) is a by-product of polyvinyl chloride (PVC), polyvinyl alcohol and acetylene production. CCR is formed through the hydrolysis of calcium carbide, as shown by the [...]

Hydraulic fracturing is a potential cause of leakage of earth dams or loss of fluid in drilling and field permeability testing. The effect of hydraulic fracturing on soil grouting is also a major concern. Although hydraulic fracturing has been adopted for decades by the petroleum industry for oil recovery in rock formations, studies on fracturing in soils are relatively few and inconclusive. The aim of this study is to provide further insight into the mechanism of hydrofracturing in soils through a field grouting trial and numerical simulation. We observe hydraulic fracturing in soils during this field trial as predicted by generally accepted groutability requirements. The hydraulic fractures are found vertically developed up to the ground surface. Numerical simulations show the hydraulic fracturing is easier to be initiated in anisotropic stress conditions, where the minor principal stress is the key factor. Numerical simulations also demonstrate significant compressions and shears during injection, suggesting the mechanism of fracturing in soils would be a shearing type. Based on this study, we propose a punching and splitting mode for the hydrofracturing in soils. The equation associated with estimating fracturing pressure is verified, and the results are found to be in good agreement with the cases examined. Key words: hydraulic fracturing, fracturing pressure, soil grouting, field testing and monitoring, numerical simulation. La fracturation hydraulique peut provoquer des fuites sur les barrages en terre ou une perte de fluide lors de forages ou d'essais de permeabilite sur le terrain. Ce procede pose egalement un probleme important, car il reduit l'efficacite de l'injection de coulis de ciment dans le sol. Bien que l'industrie petroliere recoure depuis des decennies a la fracturation hydraulique pour recueillir le petrole present dans les formations rocheuses, les etudes portant sur ce procede sont peu nombreuses et non concluantes. La presente etude vise a mieux comprendre le mecanisme de l'hydrofracturation des sols par l'intermediaire d'un essai d'injection de coulis et d'une simulation numerique. Nous observons que la fracturation hydraulique des sols se deroule conformement aux predictions basees sur les criteres d'injectabilite couramment acceptes. On constate que les fractures hydrauliques se forment verticalement et atteignent la surface du sol. Les simulations numeriques montrent que la fracturation hydraulique est plus facilement amorcee dans des conditions de contrainte anisotropes, ou la contrainte principale mineure constitue le facteur cle. En outre, des simulations numeriques mettent en evidence des phenomenes de compression de cisaillement de forte intensite durant l'injection, ce qui montre que le mecanisme de fracturation des sols est probablement de type cisaillement. A partir de la presente etude, nous proposons un mode d'hydrofracturation des sols de type << perforationfracturation >>. L'equation associee a ce mode et permettant d'estimer la pression de fracturation est verifiee et l'on constate que les resultats qu'elle fournit coincident bien avec ceux associes aux exemples etudies. [Traduit par la Redaction] Mots-cles: fracturation hydraulique, pression de fracturation, injection de coulis dans le sol, surveillance et essais sur le terrain, simulations numeriques., Introduction Hydraulic fracturing is a potential threat to the leakage of earth dams and the loss of fluid during borehole drilling and field permeability testing (Bjerrum et al. 1972; Jaworski [...]