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Workers are often required to enter unsupported trenches during the construction process, which may present serious risks. Trench failures can result in death or damage to adjacent properties; therefore, trenches should be excavated with extreme precaution. Critical height (i.e., maximum depth that can be excavated without failure) is the most important design consideration for ensuring the stability of unsupported trenches. Because excavation work is often done in the vadose zone, the influence of matric suction should be taken into account when estimating the critical height of an unsupported trench. In this study, an attempt was made to estimate the critical heights of unsupported trenches using three distinct approaches: (i) analytical method based on the extended Rankine earth pressure theory, (ii) finite element coupled stress--pore-water pressure analysis, and (iii) limit equilibrium method (i.e., Bishop's simplified and Morgenstern-Price method). It was assumed that the trenches were excavated in an engineered sand (Unimin 7030) and Indian Head till, which represent cohesionless and cohesive soils, respectively, considering various practical scenarios. Geotechnical modeling software, GeoStudio (ver. 2016; SIGMA/W and SLOPE/W), was used for both finite element analysis and the limit equilibrium method. Key words: unsupported trench, critical height, vadose zone, extended Rankine earth pressure theory, coupled analysis, limit equilibrium method, soil-water characteristic curve, matric suction. Les travailleurs sont souvent obliges d'entrer dans des tranchees non supportees pendant le processus de construction, ce qui peut presenter des risques graves. Les ruptures de tranchee peuvent entrainer la mort ou des dommages aux proprietes adjacentes. Par consequent, les tranchees doivent etre excavees avec une extreme prudence. La hauteur critique (c'est- a-dire la profondeur maximale excavee sans defaillance) est la consideration de conception la plus importante pour assurer la stabilite des tranchees non etayees. Etant donne que les travaux d'excavation sont souvent effectues dans la zone vadose, l'influence de succion matricielle doit etre prise en compte lors de l'estimation de la hauteur critique d'une tranchee non supportee. Dans cette etude, trois approches ont ete utilisees pour estimer les hauteurs critiques des tranchees non supportees: (i) methode analytique basee sur la theorie de la pression de la terre de Rankine, (ii) analyse numerique (analyse couplee des contraintes et de la pression interstitielle) et (iii) methode de l'equilibre limite (methodes simplifiees de Bishop et de Morgenstern-Price). Il a ete suppose que les tranchees soient excavees dans un sable artificiel (Unimin 7030) et un till d'Indian Head, qui representent des sols sans cohesion et cohesifs, respectivement, envisageant divers scenarios pratiques. Le logiciel de modelisation geotechnique GeoStudio (ver. 2016; SIGMA/W et SLOPE/W) a ete utilise a la fois pour l'analyse numerique et pour la methode de l'equilibre limite. Mots-cles: tranchee non supportee, hauteur critique, zone vadose, theorie de la pression de la terre de Rankine etendue, analyse couplee, methode de l'equilibre limite, courbe caracteristique sol-eau, succion matricielle., Introduction Most engineering projects involving foundations, landfills, pipelines, storm drains, etc. are initiated with an excavation for infrastructure to be installed. Workers are often required to enter the excavation or [...]

In geotechnical engineering practice, unsupported vertical trenches are typically excavated in unsaturated soils. In this case, the variation of shear strength and hydraulic conductivity with respect to soil suction is key information to analyze the stability of an unsupported vertical trench. Most shear strength and hydraulic conductivity models use the soil-water characteristic curve (SWCC) as a main tool. Various models are available to determine SWCC, shear strength, and hydraulic conductivity for unsaturated soils. Scholars or practitioners use one the existing models in numerical analyses to estimate the stability of unsupported vertical trench considering rainfall events. However, limited studies have been undertaken to investigate the effect of SWCC and hydraulic conductivity functions on the stability of unsupported vertical trenches in unsaturated soils. In the present study, numerical stability analyses are carried out by using different SWCCs and hydraulic conductivity functions to investigate their influence on the estimated safe height and stand-up time of unsupported vertical trenches. The same shear strength model was used for entire numerical analyses.

This study investigates the predictive value of preoperative ultrasonography for the presence of an intracompartmental septum and the effect of a septum on clinical outcomes and complications in patients who underwent endoscopic first extensor compartment release for de Quervain's syndrome. A total of 170 patients (181 wrists) were examined, and a septum was present in 118 (69%) patients. The sensitivity and specificity of the preoperative ultrasonography were 88% and 94%, respectively. Patients were assessed at a minimum of 12 months after endoscopic release. The Disabilities of Arm, Shoulder and Hand score (54 to 4.2), visual analogue scale pain score (8.0 to 1.0) and pinch strength (2.3 to 3.2 kg) were significantly improved compared to the preoperative status (p < 0.001). There were no significant differences in clinical outcomes or complications between patients with and without a septum. Level of evidence: IV [ABSTRACT FROM AUTHOR]

Buried pipeline systems form vital infrastructure, all over the world, to transport resources such as water, oil, and gas from the production stage to the locations of consumption. Failure or rupture in pipelines in general and oil or gas pipelines in particular lead to not only economic losses that are expensive, but also cause extensive damage to the environment in several scenarios. One of the key reasons for buried pipeline systems failure is associated with excavation or soil trenching within the proximity of pipelines. Soil deformation associated with excavation causes relative displacement between the pipeline and the surrounding soil, which contributes to external as well as internal stresses and strains on the pipelines. In this study, numerical analyses are carried out to investigate the behaviors of buried rigid and flexible pipelines by extending the effective stress analysis and the modified effective stress analysis approaches for saturated and unsaturated soils, respectively. The pipe displacement, strains, and internal force results from the study suggest that soil trenching in unsaturated soils contribute to limited deformations within the proximity of the embedded pipelines and result in lower internal forces. The proposed methodology can be used to determine the safe depths of unsupported excavations in unsaturated soils without causing excessive strains or internal forces in the ring of rigid and flexible pipes.Key words: buried pipelines, unsupported excavation, stresses, strains, unsaturated soils, finite-element analysis.Les reseaux de conduites souterraines constituent une infrastructure vitale, partout dans le monde, pour transporter des ressources telles que l'eau, le petrole et le gaz de l'etape de la production vers les lieux de consommation. Les defaillances ou les ruptures dans les conduites en general et dans les oleoducs et les gazoducs en particulier entrainent non seulement des pertes economiques qui sont couteuses, mais causent egalement des dommages importants a l'environnement dans plusieurs scenarios. L'une des principales raisons de la defaillance des conduites souterraines est liee a l'excavation ou a la tranchee du sol a proximite des conduites. La deformation du sol associee a l'excavation entraine un deplacement relatif entre la conduite et le sol environnant, ce qui contribue aux contraintes externes et internes et aux deformations des conduites. Dans cette etude, des analyses numeriques sont effectuees pour etudier les comportements des conduites rigides et flexibles souterraines developpant les approches d'analyse des contraintes effectives et d'analyse des contraintes effectives modifiees pour les sols satures et non satures, respectivement. Les resultats de l'etude concernant le deplacement, les deformations et les forces internes des tuyaux suggerent que le creusement du sol dans les sols non satures contribue a des deformations limitees a proximite des conduites integrees et entraine une reduction des forces internes. La methodologie proposee peut etre utilisee pour determiner la profondeur securitaire des excavations non soutenues dans les sols non satures sans causer de deformations excessives ou de forces internes dans l'anneau des tuyaux rigides et flexibles. [Traduit par la Redaction]Mots-cles : conduites souterraines, excavation non soutenue, contraintes, deformations, sols non satures, analyse en elements finis., IntroductionPipeline systems are built from polyethylene, plastic or steel pipes that extend over several millions of kilometres to transport or distribute water and petroleum products all over the world (Grigoryev [...]

A typical deep geological repository (DGR) design consists of a multi-barrier system, including the natural host rock and the engineered barrier system. Understanding the swelling behavior of bentonite-based sealing materials (BBSM), as a candidate material for the engineered barrier system, is crucial for DGR's long-term safety. In this study, a hydromechanical (HM) column-type test was designed to model the hydration of BBSM from the underground water and determine the resulting swelling pressure in vertical and radial directions. Five hydration tests were carried out on identical compacted samples of 70% bentonite and 30% sand (70-30 bentonite-sand) mixtures with a dry density of 1.65 g/cm3 for varied durations of hydration, between 1 day and 120 days. The experiments were performed parallel to the compaction direction. Following each HM column-type test, the advancement of the wetting front was determined for each test. After 120 days, 56,339 mm3 of water infiltrated the sample and the wetting front reached over 50% of the sample height. The evolution of axial swelling pressure revealed an initial increase in swelling pressure with time in all tests, followed by a reduction in the rate at later times. After early stages of swelling, radial sensors showed an increase in swelling pressure. After 120 days, the radial pressure sensor closest to the hydration front showed 52% more radial pressure than the axial swelling pressure. [ABSTRACT FROM AUTHOR]

Evidence supporting the implementation of three-dimensional (3D) slope stability analysis in geotechnical engineering practice has been mounting since the nineteen-seventies. Current levels of computational power and its accessibility has allowed researchers to investigate the significance of the 3D numerical analysis output compared to conventional 2D limit equilibrium approach. This study compares results of stability analyses of unsupported vertical cuts in the vadose zone using both 2D (GeoStudio 2019 R2) and 3D (FLAC3D) software. Numerical analyses are carried out for various dimensions of unsupported vertical cuts excavated in an unsaturated glacial till. The findings from two different methods (i.e. 2D and 3D) and the limitations of 2D stability analysis are discussed.

The bearing capacity and settlement of foundations are determined experimentally or modelled numerically based on conventional soil mechanics for saturated soils. In both methods, bearing capacity and settlement are estimated based on the applied vertical stress versus surface settlement relationship. These methods are also conventionally used for soils that are in an unsaturated condition, ignoring the contribution of matric suction. In this study, a methodology is proposed to estimate the bearing capacity and settlement of shallow foundations in unsaturated sands by predicting the applied vertical stress versus surface settlement relationship. The proposed method requires soil parameters obtained under only saturated conditions (i.e., effective cohesion, effective internal friction angle, and modulus of subgrade reaction from model footing test) along with the soil-water characteristic curve (SWCC). In addition, finite element analyses are undertaken to simulate the applied vertical stress versus surface settlement relationship for unsaturated sands. The proposed method and finite element analyses are performed using an elastic--perfectly plastic model. The predicted bearing capacities and settlements from the proposed method and finite element analyses are compared with published model footing test results. There is good agreement between measured and predicted results. Key words: unsaturated soil, model footing tests, settlement, bearing capacity, elastic--perfectly plastic model, finite element analysis. La capacite portante et le tassement de fondations sont determines experimentalement ou numeriquement d'apres le modele classique de la mecanique des sols pour les sols satures. Pour les deux methodes, la capacite portante et le tassement sont estimes d'apres la relation entre la contrainte normale verticale appliquee en fonction du tassement de surface. Ces methodes sont egalement utilisees conventionnellement pour les sols qui sont dans un etat non sature en ignorant la contribution de la succion matricielle. Dans la presente etude, une methodologie est proposee afin d'estimer la capacite portante et le tassement des fondations peu profondes dans les sols sableux non satures en predisant la relation entre la contrainte verticale appliquee et le tassement de surface. La methode proposee ne requiert que les parametres du sol obtenus sous des conditions saturees (c.-a-d. cohesion effective, angle de friction interne effectif, et module de reaction du sol obtenu lors d'essais de semelle a echelle reduite) ainsi que sa courbe de retention d'eau (<< SWCC >>). En outre, des analyses par elements finis sont egalement entreprises afin de simuler la relation entre la contrainte verticale appliquee et le tassement de surface de sols sableux non satures. La methode proposee et les analyses par elements finis sont effectuees en utilisant le modele elastique--parfaitement plastique. La capacite portante et le tassement predits par la methode propose e et l'analyse par elements finis sont compares avec les resultats publies des essais de semelles a echelle reduite. Il existe une bonne concordance entre les mesures et les resultats predits. Mots-cles : sols non satures, essais sur semelle a echelle reduite, affaissement, capacite portante, modele elastique--parfaitement plastique, analyse par elements finis., Introduction Bearing capacity and settlement are two key parameters required in the design of foundations. There are several procedures or techniques available for the interpretation of bearing capacity and settlement [...]

Soil trenching is extensively used in geotechnical, mining, tunneling and geo-environmental infrastructures. Safe height and stand-up time are two key factors that are required for the rational design of soil trenches. Rainfall infiltration has a significant influence on the safe height and stand-up time of unsaturated soil trenches since it can significantly alter the shear strength of soils by influencing the matric suction. In other words, predicting the variation of matric suction of soils associated with rainfall infiltration is vital to the design of unsaturated soil trenches. In this paper, finite element analysis is carried out to reproduce the variation of matric suction profile in unsaturated soil trenches associated with rainfall infiltration using the published results of a full scale instrumented test trench at the site of BBRI at Limelette, Belgium. The analysis results showed that the variation of matric suction in unsaturated soil trenches can be reliably estimated using the information of environmental factors such as the rainfall measurements.