Search

With a newly developed swelling pressure apparatus, swelling pressure tests were conducted to elucidate initial water content and specimen preparation method effects on swelling pressures (swelling pressure evaluation curve and equilibrium swelling pressure) of Kunigel-V1 bentonite. X-ray diffraction (XRD) tests were conducted to investigate the initial water content and specimen preparation method effects on basal spacing, including basal spacings of specimens before and after wetting. Experiments produced the following results. (1) The swelling pressure evaluation curve changed from a line with peak and valley to a line with early-stage steady rise as increasing initial water content. (2) The initial water content and specimen preparation method exerted no apparent effect on the equilibrium swelling pressure. (3) Basal spacing of the specimen before wetting was affected not only by the initial water content but also by the specimen preparation method. (4) The initial water content did not influence the basal spacing of the specimen after wetting. It was only affected by the specimen preparation method. Based on the swelling pressure evaluation curve patterns, swelling mechanisms during saturation for specimens with different initial conditions were discussed. Initial water content and specimen preparation method effects on equilibrium swelling pressure were explained carefully with basal spacings. Key words: initial water content, specimen preparation method, swelling pressures, XRD, 1. Introduction The deep geological disposal method was selected to address high-level radioactive waste (HLW) from the nuclear power industry by different countries (e.g., SKB 2011; NUMO 2022). In Japan, [...]

Vibrating-wire piezometers provide a number of advantages over the traditional hydraulic piezometer design. There are currently many methods and configurations for installing vibrating-wire piezometers, the most common being: single piezometers in sand packs (SP), multilevel piezometers in sand packs (MLSP), and fully grouted multilevel piezometers using either bentonite (FGB) or cement-bentonite grout (FGCB). This study assesses the performance of these four different installation methods at a field site possessing complex stratigraphy, including glacial and marine sediments. To accomplish this objective, pore pressure data recorded between December 2017 and July 2019 were analyzed. Data indicate that SP, MLSP, and FGB piezometers performed most reliably, because piezometers installed at the same depth with these methods recorded similar pressure variations that were coherent with the hydrogeological setting. Of the two fully grouted installations using cement-bentonite grout, one installation failed completely due to a hydraulic short circuit, likely caused by preferential flow occurring along the wires of the embedded instruments. The lack of a standard method for mixing cement-bentonite grout at the time of construction likely contributed to the failure of the FGCB installations, as the grout mixture used in this study was likely too viscous to provide a suitable seal. Key words: vibrating-wire piezometers, St. Lawrence Lowlands, fully grouted methods. Les piezometres a fil vibrant offrent un certain nombre d'avantages par rapport aux piezometres hydrauliques traditionnels. Il y a actuellement de nombreuses methodes et configurations pour installer des piezometres a fil vibrant, les plus courantes etant les suivantes : piezometres simples dans des paquets de sable (SP), piezometres multiniveaux dans des paquets de sable (MLSP) et piezometres multiniveaux entierement scelles a l'aide de bentonite (FGB) ou de coulis de ciment-bentonite (FGCB). Cette etude evalue les performances de ces quatre methodes d'installation differentes sur un site de terrain presentant une stratigraphie complexe, comprenant des sediments glaciaires et marins. Pour atteindre cet objectif, les donnees de pression interstitielle enregistrees entre decembre 2017 et juillet 2019 ont ete analysees. Les donnees indiquent que les piezometres SP, MLSP et FGB ont donne les resultats les plus fiables, car les piezometres installes a la meme profondeur avec ces methodes ont enregistre des variations de pression similaires, coherentes avec le contexte hydrogeologique. Parmi les deux installations entierement scellees a l'aide d'un coulis de ciment-bentonite, l'une d'elles s'est completement effondree en raison d'un courtcircuit hydraulique, probablement cause par un ecoulement preferentiel le long des fils des instruments encastres. L'absence d'une methode standard pour le melange de coulis de ciment-bentonite au moment de la construction a probablement contribue a l'echec des installations de BGCF, car le melange de coulis utilise dans cette etude etait probablement trop visqueux pour assurer une etancheite adequate. [Traduit par la Redaction] Mots-cles : piezometres a fil vibrant, basses terres du Saint-Laurent, methodes a scellement complet., 1. Introduction In the province of Quebec, 89% of the population of the province lives within the depositional extent of the Champlain Sea sediments, which were deposited by a marine [...]

A method for determination of the active earth pressure exerted by a cohesionless backfill, subjected to water seepage from a high water table, on a retaining structure is presented. The method comprises a numerical procedure based on the boundary element method (BEM) for the seepage analysis and a trial wedge method for the limit equilibrium analysis. The numerical results of the seepage analysis are presented as normalized charts that can be used in the trial wedge method without recourse to the BEM computer code. The main benefits of the proposed analysis are the simplicity of use and the small amount of data necessary. For the seepage analysis, only the phreatic line exit point height at the retaining structure face is required. Numerical results obtained for a proposed example of a retaining wall show the influence of the water seepage on the active earth pressure. The analysis method also can deal with cases of soil anisotropy with respect to the permeability. Key words: earth pressure, water seepage, retaining structures, limit equilibrium, boundary element method. On presente ici une methode permettant de determiner la pression active des terres exercee par un remblai sans cohesion, soumis a une infiltration d'eau provenant d'une nappe phreatique dont le niveau est eleve, sur un ouvrage de soutenement. La methode comporte une approche numerique basee sur la methode des elements finis de frontiere (MEFF) et servant a analyser l'infiltration d'eau une methode d'essai sur coins de sol permettant d'effectuer l'analyse de l'equilibre limite. Les resultats obtenus a l'aide de la methode numerique d'analyse de l'infiltration sont presentes sous la forme de diagrammes normalises, que l'on peut utiliser dans le cadre de la methode d'essai sur coins sans avoir recours au programme informatique base sur la MEFF. L'analyse proposee a pour principaux avantages d'etre simple a utiliser et de ne necessiter que peu de donnees. L'analyse de l'infiltration necessite seulement de connaitre la hauteur du point de sortie de la surface de la nappe phreatique sur la paroi de l'ouvrage de soutenement. Les resultats obtenus a l'aide de la methode numerique dans le cas de l'exemple de mur de soutenement propose mettent en evidence l'influence de l'infiltration d'eau sur la pression active des terres. La methode d'analyse proposee permet egalement d'etudier la permeabilite des sols anisotropes. [Traduit par la Redaction] Mots-cles: pression des terres, infiltration d'eau, ouvrages de soutenement, equilibre limite, methode des elements finis de frontiere., Introduction The presence of water in soil voids has a large influence on the lateral earth pressure on soil retaining structures. The hydrostatic pressure due to water accumulation behind the [...]

A numerical method is developed to evaluate the passive earth pressure coefficients for an inclined rigid retaining wall resting against a horizontal cohesionless backfill. A composite failure surface comprises a log spiral, and its tangent is assumed in the present study. The unique failure surface is identified based on the limit equilibrium approach coupled with the Kotter equation (published in 1903). Force equilibrium conditions are used to evaluate the magnitude of the passive thrust, whereas the moment equilibrium condition is employed to determine the location of the passive thrust. The distinctive feature of the present study is that no assumption is required to be made regarding the point of application of the passive thrust, which would otherwise be an essential criterion with respect to the several limit equilibrium based investigations available in the literature. The passive earth pressure coefficients, [K.sub.pγ], are evaluated for various values of soil frictional angle φ, wall frictional angle δ, and wall inclination angle γ, and compared with the existing results. Key words: inclined retaining wall, cohesionless backfill, Kotter equation, limit equilibrium, passive earth pressure coefficients, passive thrust location. Une methode numerique est developpee pour evaluer les coefficients de pression passive des terres d'un mur de soutenement incline rigide s'appuyant contre un remblai sans cohesion horizontal. Dans la presente etude, on prend l'hypothese d'une surface de rupture composite comportant une spirale logarithmique et sa tangente. Cette surface de rupture unique est determinee a partir de la methode de l'equilibre limite couplee a l'equation de Kotter (publie en 1903). Les conditions d'equilibre des forces sont utilisees pour evaluer l'amplitude du chevauchement passif, tandis que la condition d'equilibre des moments sert a localiser ce dernier. La singularite de la presente etude vient du fait qu'il n'est pas necessaire de formuler une hypothese concernant le point d'application du chevauchement passif, alors que ce dernier constitue un critere essentiel dans les quelques etudes basees sur l'equilibre limite disponibles dans la litterature. Les coefficients de pression passive des terres, [K.sub.yγ], sont evalues pour differentes valeurs d'angle de frottement du sol φ, d'angle de frottement du mur δ et d'angle d'inclinaison du mur γ, puis sont compares avec les resultats existants. [Traduit par la Redaction] Mots-cles : mur de soutenement incline, remblai sans cohesion, equation de Kotter, equilibre limite, coefficients de pression passive des terres, localisation du chevauchement passif., Introduction A study on earth pressures is an interesting topic in the field of geotechnical engineering. Numerous investigators have been working in this research area, as understanding the behaviour of [...]

This paper describes a method developed to link the measured piezocone dissipation excess pore-water pressure (Δu) to the soil undrained shear strength ([s.sub.u]). In cohesive soils, both Δu and [s.sub.u] are dependent on the same variables (compressibility, stress state, stress history), which allows them to be related by the theoretical cavity expansion--critical state framework. A mathematical derivation is presented to demonstrate that the ratio of normalized maximum excess pore pressure and the normalized undrained shear strength fluctuates around a mean value, being affected by soil strength and compressibility and independent of stress history. The predicted [s.sub.u] values obtained from the proposed approach are calibrated against field vane shear strength in both normally consolidated (monotonic dissipation tests) and overconsolidated soils (dilatory dissipation tests). Reported results are consistent and encourage the use of the method in engineering practice. On a routine basis, [s.sub.u] estimated from pore pressure can be compared with values predicted from penetration resistance, adding desired redundancy for purposes of error detection when interpreting cone penetration testing with pore pressure measurement (CPTU) data. Key words: excess pore-water pressure, undrained shear strength, dissipation tests, cone penetration testing with pore pressure measurement (CPTU). Le present article decrit une methode nouvellement elaboree permettant de relier les mesures de la dissipation de l'exces de pression interstitielle de l'eau dans les pores a l'aide d'un piezocone (Δu) a la resistance au cisaillement non draine du sol ([s.sub.u]). Dans les sols cohesifs, Δu et [s.sub.u] dependent des memes variables (compressibilite, etat de contrainte, historique des contraintes) et peuvent etre reliees dans un cadre theorique combinant l'expansion de cavite avec l'etat critique. Une derivation mathematique est exposee afin de demontrer que le rapport entre l'exces maximum normalise de pression interstitielle dans les pores et la resistance normalisee au cisaillement non draine oscille autour d'une valeur moyenne sous l'influence de la resistance et de la compressibilite du sol et independamment de l'historique des contraintes. Les valeurs predites de [s.sub.u] obtenues a partir de la methode proposee sont ajustees par rapport aux mesures scissometriques de resistance au cisaillement effectuees sur le terrain, dans le cas des sols normalement consolides (essais monotones de dissipation) et surconsolides (essais de dissipationdilatation). Les resultats obtenus sont coherents et encouragent les ingenieurs a mettre cette methode en pratique. On peut comparer de fa^on systematique les valeurs de la [s.sub.u] determinees a partir de la pression dans les pores a celles predites a partir de la resistance a la penetration tout en ajoutant la redondance souhaitee afin de reperer les erreurs d'interpretation des donnees des essais de penetration du cone avec la mesure des pressions interstitielle (CPTU). [Traduit par la Redaction] Mots-cles: exces de pression interstitielle de l'eau, resistance au cisaillement non draine, essais de dissipation, essais de penetration du cone avec la mesure des pressions interstitielle (CPTU)., Introduction Prediction of soil properties from piezocone test (cone penetration testing with pore pressure measurement, CPTU) data in cohesive soils is routinely carried out in geotechnical design. This is possible [...]

Methods of computation for soil heave based on an 'equivalent' net normal stress path approach often have built-in assumptions regarding the relationship between in situ matric suction, overburden stress, and swell pressure. The term 'matric suction equivalent' has been previously defined as the difference between in situ state of stress projected on the net normal stress plane (represented by swell pressure) and overburden stress. Correlations between matric suction, overburden stress, and swell pressure for matric suction values in excess of the air-entry value have not been well studied and are explored here for expansive soils. Filter paper (in-contact) and constant volume swell pressure tests were performed on undisturbed tube samples of expansive soils taken from Arizona, Colorado, and Texas. In general, the ratio of the matric suction equivalent to the matric suction decreases with increasing soil suction. An empirical relationship was established in which the matric suction equivalent was found to be proportional to the logarithm of the matric suction for in situ matric suctions greater than a certain value, termed as the 'intercept matric suction'. A correlation between the intercept matric suction and the soil's plasticity index (PI) was found for the clays of this study. The developed correlations represent a method for obtaining approximate estimates of in situ matric suction for expansive soils from PI and swell pressure data. Implications of the study findings for the use of an equivalent net normal stress approach for estimation of soil heave are explored. Key words: expansive soils, unsaturated soils, matric suction, matric suction equivalent, swell pressure, degree of saturation, heave prediction. Les methodes de calculs de soulevement de sol basees sur une approche avec contrainte normale nette << equivalente >> comportent souvent des hypotheses sur le lien entre la succion matricielle in situ, la pression lithostatique et la pression de gonflement. Le terme<>a ete precedemment defini comme la difference entre l'etat de contrainte in situ projete sur le plan de la contrainte normale nette (representee par la pression de gonflement) et la pression lithostatique. Les liens entre la succion matricielle, la pression lithostatique et la pression de gonflement pour les valeurs de succion matricielle depassant la charge capillaire critique n'ont pas encore ete formellement etudies et sont examines ici dans le cas des sols expansifs. Des essais de pression de gonflement sur papier filtre (en contact avec les echantillons) et a volume constant ont ete realises sur des tubes d'echantillons non perturbes de sols expansifs preleves en Arizona, au Colorado et au Texas. De fa^on generale, le quotient de l'equivalent succion matricielle par la succion matricielle diminue lorsque la succion du sol augmente. Une relation empirique a montre que l'equivalent succion matricielle semblait etre proportionnel au logarithme de la succion matricielle dans le cas ou cette derniere etait superieure a une certaine valeur qualifiee de << succion matricielle au point d'intersection >>. Une correlation entre la succion matricielle au point d'intersection et l'indice de plasticite (IP) du sol a ete decouverte dans le cas des argiles etudiees ici. Les correlations ainsi mises en evidence constituent une methode permettant d'obtenir des estimations approximatives de la succion matricielle in situ dans le cas des sols expansifs a partir des valeurs de l'IP et de la pression de gonflement. On evoque enfin les repercussions des decouvertes realisees dans la presente etude sur l'utilisation d'approches avec contrainte normale nette equivalente pour estimer le soulevement des sols. [Traduit par la Redaction] Mots-cles: sols expansifs, sols non satures, succion matricielle, equivalent succion matricielle, pression de gonflement, degre de saturation, prediction du soulevement., Introduction The vertical swelling of an expansive soil layer is generally referred to as heave. Existing methods for computing heave in response to soil wetting typically follow either an actual [...]

In reservoir engineering, an oil reservoir is commonly modeled using Darcy's diffusion equation for a porous medium. In this work we propose a fractional diffusion equation to model the pressure distribution, p(x, t), of fluid in a horizontal one-dimensional homogeneous porous reservoir of finite length, L, and uniform thickness. A chief concern in this work is to examine the sensitivity of the pressure distribution, p(x, t), to different forms of pseudo-diffusivity, K, including cases when it depends upon the order of the fractional derivative (α), 0 [less than or equal to] α < 1 (e.g., K [varies] (1 - α)), which may be more realistic for some types of rock formations. In all cases the systems show a near-linear increase in the pressure difference P(x, t) = (p(x, t) - [p.sub.i])/[p.sub.i] in the reservoir for large times, where [p.sub.i] = p(x, t = 0). For x/L < 0.4, the rate of increase of P with time increases with a, but there is a crossover at x/L = 0.4 and this trend reverses for x/L > 0.4. When K = 10k (k is the conventional permeability when α = 0), the solutions are almost independent of a, and when K = 0.1k the rate of increase in P depends upon α. This effect is enhanced when K = (1 - α)k; furthermore, in this case towards the closed end of the reservoir the pressure distribution remains practically undisturbed as α [right arrow] 1. These results show that the pressure distribution in a porous reservoir is very sensitive to the dependence of the pseudo-diffusivity on the order of the fractional derivative, α. PACS Nos.: 47.56.+r, 91.60.Np, 91.60.Tn, 91.65. En ingenierie des reservoirs, un reservoir d'huile est communement modele en utilisant l'equation de diffusion de Darcy pour un milieu poreux. Nous proposons ici une equation de diffusion fractionnaire pour modeliser la distribution de pression p(x, t) d'un fluide dans un reservoir unidimensionnel poreux horizontal de longueur L et d'epaisseur uniforme. Notre premier but est d'examiner la sensitivite de la distribution de pression p(x, t) a differentes formes de la pseudo-diffusivite K, incluant des cas ou elle depend de l'ordre de la derivee fractionnaire (α), 0 ≤ α [less than or equal to] 1 (i.e., K [varies] (1 - α)), qui peut etre plus realiste pour certains types de formation rocheuse. Dans tous les cas, le systeme montre une croissance quasi lineaire dans la difference de pression P(x, t) = (p(x, t) - [p.sub.i])/[p.sub.i] pour des temps longs, la ou [p.sub.i] = p(x, t = 0). Pour x/L < 0,4, le taux de croissance de P avec le temps augmente avec a, mais ilyaun croisement a x/L = 0.4 et cette tendance se renverse pour x/L > 0,4. Lorsque K = 10k (k est la permeabilite conventionnelle lorsque α = 0), les solutions deviennent pratiquement independantes de a et lorsque K = 0,1k, le taux d'augmentation de P depend de α. Cet effet est encore plus grand lorsque K = (1 - α)k et dans ce cas, la pression au bout du reservoir demeure pratiquement inchangee lorsque α → 1. Ces resultats montrent que la distribution de pression dans un reservoir poreux est tres sensible a la dependance de la pseudo-diffusivite sur l'ordre a de la derivee fractionnaire. [Traduit par la Redaction], 1. Introduction Transport of particles and scalar fields in different types of media has many applications in engineering and mathematical sciences, from diffusion in pipes to atmospheric dynamics and blood [...]

The hole erosion test (HET) is used in the study of soil erosion in the case of what is known as 'piping' when concentrated leaks occur. The HET enables the determination of soil erosion characteristics such as the critical shear stress along the pre-formed hole (pipe) and the coefficient of soil erosion. Normally, in the HET, the hydraulic gradient is determined from the difference between the piezometric heads measured at the inflow and outflow chambers (upstream and downstream of the soil specimen). Hydraulic analysis shows that such measurements ignore losses at the entrance and exit of the hole, causing the overestimation of the hydraulic gradient along the length of the hole, and thus the calculated shear stress. In this technical note, the results of preliminary analysis using the Bernoulli principle and of numerical study of the pressure conditions in the HET apparatus are shown. The turbulent flow in the HET apparatus was calculated using ANSYS commercial CFD (computational fluid dynamics) software. The analysis was performed for various hole entrance shapes. The conclusion of this note details the differences between traditionally determined hydraulic gradients and those numerically derived along the length of a hole. Key words: hole erosion test, piping, hydraulic gradient, shear stress, Bernoulli principle, turbulent flow modelling. L'essai d'erosion d'un trou (EET) est utilise pour etudier l'erosion du sol dans un cas connu en tant que << renard >>, lorsque des fuites concentrees se produisent. L'EET permet de determiner les caracteristiques d'erosion du sol, tels que la contrainte de cisaillement critique le long du trou preforme (renard) et le coefficient d'erosion du sol. Normalement, lors d'un EET le gradient hydraulique est determine a partir de la difference de tete piezometrique mesuree dans les chambres d'entree et de sortie (en amont et en aval de l'echantillon de sol). L'analyse hydraulique demontre que de telles mesures ignorent les pertes a l'entree et a la sortie du trou, ce qui surestime le gradient hydraulique le long du trou, donc la contrainte de cisaillement calculee. Dans cette note technique, on presente les resultats d'une analyse preliminaire a partir du principe de Bernouilli et une etude numerique des conditions de pression dans l'appareil d'EET. L'ecoulement turbulent dans l'appareil d'EET a ete calcule avec le logiciel de DCF (dynamique computationnelle des fluides) commercial ANSYS. L'analyse a ete realisee pour differentes formes d'entree de trou. La conclusion de cette note presente en details les differences entre les gradients hydrauliques determinees a l'aide des methodes traditionnelles de ceux derives numeriquement le long du trou. [Traduit par la Redaction] Mots-cles: essai d'erosion d'un trou, renard, gradient hydraulique, contrainte de cisaillement, principe de Bernouilli, modelisation d'ecoulement turbulent., Introduction Earth hydraulic structures (e.g., dams or levees) and their sub-bases can be eroded by seeping water. The failure of such structures while they are permanently or temporarily retaining water [...]

The polymer air-drawing model of polyethylene terephthalate spunbonding nonwovens and the air jet flow field model in wide slot positive pressure spunbonding process have been established. The influence of the density and the specific heat capacity of polymer melt at constant pressure changing with polymer temperature on the fiber diameter have been studied, which is solved by introducing the numerical computation results of the air jet flow field of attenuator. It is simulated by means of the finite difference method. The predicted fiber diameter agrees with the experimental data. The effects of the processing parameters on the fiber diameter with the help of the image analysis method have been investigated. A higher inlet pressure, smaller slot width, and smaller jet angle will all cause higher z-axis position of air velocity and air pressure, which are beneficial to the air drawing of the polymer melt and thus to reducing the fiber diameter. The experimental results show that the agreement between the results and experimental data is better, which verifies the reliability of these models. The results present great prospects for this research in the field of computer assisted design of spunbonding process, technology, and equipment., INTRODUCTION Spunbonding technology is used commercially as a single-step process for converting polymer resin into nonwoven web, which dates back to 1950s [1-4], in spunbonding process, a molten stream of [...]

Rubber compounds have highly viscoelastic properties. The viscoelastic behaviors that have been exhibited during die extrusion include die swell and vortices in regions of sudden contraction. In this study, the application of rheological models to the capillary die extrusion process is investigated. Experiments and simulations were conducted using a fluidity tester and finite element analysis, respectively. The velocity distributions, velocity profiles, pressure drops, and vortices at the capillary die entrance were analyzed through computer simulations for various viscoelastic models [i.e., Phan-Thien and Tanner (PTT), Giesekus, POMPOM, simplified viscoelastic, and generalized Newtonian models]. Different models exhibited different pressure drops and different velocity profiles in the capillary die. Only the full viscoelastic models (PTT, Giesekus, and POMPOM) predicted the vortex at the corner of the reservoir that is the capillary die entrance. However, the simplified viscoelastic and generalized Newtonian models did not predict the vortex. All the viscoelastic models studied in this article predicted the die swells in various ways, and these were compared with the experimental results. The PTT and simplified viscoelastic models exhibited good agreement with the experimental results of the die swells., INTRODUCTION Computer simulations are used widely in science and engineering to solve problems and understand physical behaviors. The accuracy of the simulation results depends on the numerical computations and theoretical [...]

The recent discovery of more than a thousand planets outside our Solar System (1,2), together with the significant push to achieve inertially confined fusion in the laboratory (3), has prompted a renewed interest in how dense matter behaves at millions to billions of atmospheres of pressure. The theoretical description of such electron-degenerate matter has matured since the early quantum statistical model of Thomas and Fermi (4-10), and now suggests that new complexities can emerge at pressures where core electrons (not only valence electrons) influence the structure and bonding of matter (11). Recent developments in shock-free dynamic (ramp) compression now allow laboratory access to this dense matter regime. Here we describe ramp-compression measurements for diamond, achieving 3.7-fold compression at a peak pressure of 5 terapascals (equivalent to 50 million atmospheres). These equation-of-state data can now be compared to first-principles density functional calculations (12) and theories long used to describe matter present in the interiors of giant planets, in stars, and in inertial-confinement fusion experiments. Our data also provide new constraints on mass-radius relationships for carbon-rich planets., Mass-radius data for extrasolar planets combined with equation-of-state (EOS) models for constituent materials reveal that matter at pressures of several terapascals is quite common throughout the Universe (1,2,13). At several [...]

Spinel lherzolite xenoliths within alkali basalts exposed at Rayfield River and Big Timothy Mountain, south-central British Columbia, represent samples of the underlying lithospheric mantle. Electron microprobe analysis shows that most xenoliths comprise compositionally homogeneous grains of olivine, orthopyroxene, clinopyroxene, and spinel. We applied the following mineral-pair geothermometers to these rocks: orthopyroxene-clinopyroxene, spinel-orthopyroxene, and spinel-olivine. Temperatures calculated using the Brey and Kohler calibration of two-pyroxene thermometry were constrained in pressure by being required to lie on a model geotherm we develop for this region of B.C. The model geotherm is constrained to produce a temperature at the Moho (33 km) of 825 ± 25°C to match the lowest temperature peridotite xenoliths recovered in this study. Although the overall effect of pressure on the temperature calculations is negligible (~2°C for 0.1 GPa), the simultaneous solution of the model geotherm and the pressure-dependent Brey-Kohler two-pyroxene thermometry removes the need for adopting an arbitrary pressure. We take these temperatures to represent peak mantle lithosphere temperatures. Fourteen Rayfield River xenoliths return two-pyroxene temperatures between 841 and 962°C corresponding to depths of 34-42 km. Orthopyroxene-spinel and olivine-spinel results are 889 ± 60 and 825 ± 88°C, respectively. Five Big Timothy xenoliths have two-pyroxene temperatures spanning 840- 1058°C and corresponding to depths of 34-48 km. Mean orthopyroxene-spinel and olivine-spinel temperatures are 844 ± 63 and 896 ± 232°C, respectively. We argue that the differences in ranges of temperature do not represent closure temperatures imposed during cooling either in the mantle or during transport by the magma. Rather, these differences reflect differences in the original calibrations of the geothermometers or different degrees of equilibration in exchange reactions in dry rocks. Isochemical phase diagrams (pseudosections) constrain the pressure-temperature (P-T) field in which spinel is stable. These diagrams suggest that the spinel- bearing peridotites equilibrated at pressures ranging from ~9.6 to 14 kbar (10 kbar = 1 GPa). Les xenolites de lherzolite a spinelle dans des basaltes alcalins affleurant a la riviere Rayfield et au mont Big Timothy, dans le centre-sud de la Colombie-Britannique, constituent des echantillons du manteau lithospherique sous-jacent. Des analyses par microsonde electronique montrent que la plupart des xenolites comprennent des grains d'olivine, d'orthopyroxene, de clinopyroxene et de spinelle de composition homogene. Nous avons applique les geothermometres de paires minerales suivants a ces roches: orthopyroxene-clinopyroxene, spinelle-orthopyroxene et spinelle-olivine. Les temperatures calculees en utilisant l'etalonnage de Brey et Kohler de thermometrie a deux pyroxenes etaient limitees par la pression puisqu'elles devaient se trouver sur un geotherme modele que nous avons developpe pour cette region de la Colombie-Britannique. Le geotherme modele se limite a produire une temperature au Moho (33 km) de 825 ± 25°C afin de concorder avec la plus basse temperature des xenolites a peridotite recuperes dans le cadre de cette etude. Bien que l'effet global de la pression sur les calculs de la temperature soit negligeable (~2°C pour 0,1 GPa), la resolution simultanee du modele geotherme et de la thermometrie Brey-Kohler a deux pyroxenes et dependante de la pression annule le besoin d'adopter une pression arbitraire. Selon nous, ces temperatures representent les temperatures cretes du manteau lithospherique. Quatorze xenolites de la riviere Rayfield ont donne des temperatures situees entre 841 et 962°C pour des assemblages de deux pyroxenes, ce qui correspond a des profondeurs de 34 a 42 km. Les resultats pour l'orthopyroxene-spinelle et l'olivine-spinelle sont respectivement de 889 ± 60°C et de 825 ± 88°C. Cinq xenolites de Big Timothy ont des temperatures determinees sur des assemblages de deux pyroxenes dans la plage entre 840 et 1058°C, ce qui correspond a des profondeurs de 34 a 48 km. Les temperatures moyennes pour l'orthopyroxene-spinelle et l'olivine-spinelle sont respectivement de 844 ± 63°C et de 896 ± 232°C. Selon nous, les differences dans les plages de temperatures ne representent pas les temperatures de fermeture imposees durant le refroidissement, ni dans le manteau, ni durant le transport par le magma. Ces differences sont plutot le reflet des differences dans les etalonnages originaux des geothermometres ou les differents degres d'equilibre dans les reactions d'echanges dans les roches seches. Des diagrammes de phases isochimiques (pseudosections) limitent le champ de temperature et de pression dans lequel le spinelle est stable. Selon ces diagrammes, les peridotites comportant du spinelle auraient atteint l'equilibre a des pressions variant de ~9,6 a 14 kbar (10 kbar = 1 GPa). [Traduit par la Redaction], Introduction The structure, thermal conditions, and mineralogy of the mantle lithosphere in areas of high heat flow and relatively elevated topography are of continued tectonic interest (Hyndman 2010; Hyndman and [...]

Reliable measurement of pressure within a particulate media has frustrated researchers in the field of soil mechanics and soil structure interaction for many years. The difficulty stems from the fact that most sensing systems involve compliance in the measurement concept. This compliance imparts a parasitic output to the measurement. In the past, researchers have attempted to calibrate this disturbance. Research has demonstrated that calibrations of this sort are dependent upon soil type, particle size, sensor geometry, and soil stiffness. Response of such sensors has been shown to be stress history- dependent: the response upon unloading maybe highly nonlinear, resulting in a high degree of hysteresis. Complications in the measurement of soil pressure within a soil mass are significantly more complex from those met in the measurement of soil pressure at a structural boundary and must be considered separately. This paper utilizes a concept called the Null Soil Pressure System. Null pressure sensors were embedded and tested in a series of uniformly graded soils with particle diameters ranging from less than 0.15 to 15 mm. The data indicates that the response of the null pressure sensor consistently exceeds the actual soil pressure by a value of 4% ± 3%. This outcome is seen to be independent of soil type, particle size, stiffness, and stress history. No hysteresis is noted between loading and unloading, and additional loading cycles align with that of the virgin loading segment. Key words: soil pressure measurement, granular soils, experimentation. L'obtention de mesures de pression fiables a l'interieur d'un milieu particulaire donne des maux de tete aux chercheurs dans les domaines de la mecanique des sols et de l'interaction sol-structure depuis plusieurs annees. La difficulte provient du fait que la plupart des systemes de sondes impliquent l'elasticite dans le concept de mesure. Cette elasticite ajoute un resultat parasite a la mesure. Dans le passe, les chercheurs ont tente de calibrer ce derangement. La recherche a demontre qu'un tel calibrage est dependant du type de sol, de la granulometrie, de la geometrie de la sonde et de la rigidite du sol. Les reponses de ces sondes ont ete demontrees comme etant dependantes de l'historique des contraintes, et la reponse en dechargement peut etre tres non lineaire, ce qui entrame un fort degre d'hysteresis. Les complications dans la mesure de la pression d'un sol a l'interieur d'une masse de sol sont significativement plus complexes que celles rencontrees lors de la mesure de la pression d'un sol a une frontiere structurelle, et doivent etre considerees separement. Cet article utilise un concept appele le <>. Des sondes de pression nulle ont ete enfouies et testees dans une serie de sols uniformement distribues avec des particules de diametre de moins de 0,15 a 15 mm. Les donnees indiquent que la reponse de la sonde de pression nulle excede la pression reelle du sol de fa^on consistante d'une valeur de 4 ± 3%. Ce resultat est independant du type de sol, de la granulometrie, de la rigidite et de l'historique des contraintes. Aucune hysteresis n'est observee entre le chargement et le dechargement, et les cycles de chargement additionnels sont alignes avec le segment original de chargement. [Traduit par la Redaction] Mots-cles: mesure de la pression du sol, sols granulaires, experimentation., Introduction Over recent years there has been a growing trend in geotechnical research to perform large-scale control testing or scaled centrifuge modeling to evaluate numerical and analytical computational techniques in [...]

The effect of initial particle fabric on the one-dimensional compression response of Fraser River sand was investigated. One-dimensional compression with lateral stress measurement was carried out on reconstituted Fraser River sand specimens using an instrumented oedometer. Laboratory specimens were reconstituted by air pluviation, tamping, and vibration and were prepared with an initial relative density ranging from medium loose to very dense. For Fraser River sand in one- dimensional compression, air-pluviated specimens yielded the highest values for the coefficient of lateral earth pressure at rest ([K.sub.o]), tamped specimens produced the lowest [K.sub.o] values, and vibrated specimens produced intermediate [K.sub.o] values. The results from the present study demonstrate that specimens resulting from different laboratory reconstitution methods (i.e., different initial particle fabrics) exhibit different one-dimensional compression responses and produce different [K.sub.o] values. A 'fabric factor' was introduced to account for the effect of the initial particle fabric on the measured coefficient of lateral earth pressure at rest. Using the fabric factor, the constant volume friction angle, and the specimen relative density, a new empirical equation defining the coefficient of lateral earth pressure at rest during normally consolidated loading is proposed. Key words: sand, one-dimensional compression, particle fabric, coefficient of lateral earth pressure at rest. L'effet de la structure initiale des particules de sable de la riviere Fraser sur leur comportement en compression unidimensionnelle a ete etudie. Des mesures de compression unidimensionnelle avec contraintes laterales ont ete realisees avec un odometre instrumente sur des echantillons reconstitues de sable de la riviere Fraser. Les echantillons de laboratoire ont ete reconstitues par pluviation a l'air, par pilonnage et par vibration, et ont ete prepares avec une densite relative initiale variant de moyennement lache a tres dense. Pour les echantillons de sable de la riviere Fraser en compression unidimensionnelle, les echantillons prepares par pluviation a l'air ont donne les valeurs les plus elevees du coefficient de pression laterale des terres au repos ([K.sub.o]), les echantillons pilonnes ont produit les valeurs de [K.sub.o] les plus faibles, et les echantillons vibres ont genere des valeurs de [K.sub.o] intermediaires. Les resultats de cette etude demontrent que les echantillons produits par differentes methodes de reconstitution de laboratoire (c'est-a-dire differentes structures initiales des particules) presentent des comportements en compression unidimensionnelle differents, et produisent des valeurs de [K.sub.o] differentes. Un facteur de ≪ structure des particules ≫ a ete introduit pour tenir compte de l'effet de la structure initiale des particules sur le coefficient de pression laterale des terres au repos mesure. A partir du facteur de structure des particules, de l'angle de friction a volume constant et de la densite relative de l'echantillon, une nouvelle equation empirique qui defini le coefficient de pression laterale des terres au repos durant le chargement normalement consolide est proposee. [Traduit par la Redaction] Mots-cles: sable, compression unidimensionnelle, structure des particules, coefficient de pression laterale des terres au repos., Introduction The coefficient of lateral earth pressure at rest, [K.sub.o], is used to define the stress state in soil where no lateral deformation occurs. [K.sub.o] is expressed as the ratio [...]

This paper investigates the magnitude and distribution of earth pressure on a support system in open cuts in jointed rock mass for the safer and more economical design and construction of earth-retaining structures installed in a rock stratum. The paper first investigates the limitations of previous research on earth pressure and then addresses them to provide a numerical parametric study based on the discrete element method, which can consider the joint characteristics of a rock stratum. The controlled parameters include rock type, joint conditions (shear strength and angle of joints), and wall type. The magnitude and distribution of earth pressure are investigated based on interactions between the ground and the retaining structure. In addition, earth pressure in the rock stratum is compared with Peck's earth pressure for soil ground. The results indicate that the magnitude and distribution of earth pressure in jointed rock mass are strongly influenced by rock type, joint conditions, and wall type, and that this pressure can be very different from that in soil ground. Furthermore, the results of numerical tests are compared with field measurements, and the comparison shows a reasonable agreement. This paper provides useful data for the assessment of earth pressure in designing support systems for jointed rock mass. Key words: rock excavation, support system, earth pressure, joint condition, soil-structure interaction, wall type. Cet article investigue la magnitude et la distribution de la pression des terres sur le systeme de support dans ouvertures dans des masses rocheuses jointees, dans l'optique d'une conception et construction plus securitaire et plus economique de structures de retention installees dans une couche de roche. L'article presente l'etude des limites des recherches anterieures sur la pression des terres, pour ensuite y repondre a l'aide d'une etude numerique parametrique basee sur la methode des elements discrets, qui peut considerer les caracteristiques jointes d'une couche de roche. Les parametres controles incluent le type de roche, les conditions des joints (la resistance au cisaillement et l'angle des joints), et le type de face. La magnitude et la distribution de la pression des terres sont evaluees selon les interactions entre le sol et la structure de retention. De plus, la pression des terres dans la couche de roche est comparee avec la pression des terres de Peck pour le sol. Les resultats indiquent que la magnitude et la distribution de la pression des terres dans la masse de roche jointee sont fortement influencees par le type de roche, les conditions des joints et le type de face, et que cette pression peut etre tres differente de celle dans un sol. En outre, les resultats des essais numeriques sont compares avec des mesures de terrain, et la comparaison demontre une correspondance raisonnable. Cet article offre des donnees utiles pour l'evaluation de la pression des terres dans la conception de systemes de support pour une masse de roche jointee. [Traduit par la Redaction] Mots-cles: excavation dans la roche, systeme de support, pression des terres, condition des joints, interaction sol- structure, type de face., Introduction Various ground excavation works in complex urban areas can give rise to several problems for surrounding environments. In particular, miscalculating earth pressure on excavation walls may cause the collapse [...]

Two cast-in-place reinforced concrete box culverts (Longs Creek and McBean Brook culverts) with similar geometry were instrumented to monitor earth pressures. The Longs Creek structure is a 7.30 m wide by 4.53 m high double-cell box under 14.10 m of fill, constructed using the positive projection installation (PPI) method. The McBean Brook structure is a 6.75 m wide by 4.65 m high double-cell box culvert under 25.10 m of fill, constructed using the induced trench installation (ITI) method. Earth pressures were monitored as the fill height above the culvert was increased for both structures. Data from the McBean Brook culvert at a fill height of 14.40 m are compared with the data from the Longs Creek culvert. The similar geometries of these two prototype culverts provide a unique opportunity to compare their performance based on the two different installation methods. For a comparable height of soil cover, measured vertical earth pressures on the roofs were 0.94 and 0.56 times the overburden pressures for the Longs Creek (PPI) and the McBean Brook (ITI) culverts, respectively. The average measured lateral earth pressure was 0.32 times the overburden pressure at the Longs Creek culvert (PPI), and 0.46 times the overburden pressure at the McBean Brook culvert (ITI). Data from the McBean Brook culvert pertaining to base contact pressure are also presented, but could not be compared directly with the Longs Creek culvert, as base pressures were not measured. Measured pressures at the base of the McBean Brook culvert show the presence of drag forces developed on the sidewalls of box culverts. Results from centrifuge model testing are also presented and compared with the field-measured pressures. Key words: induced trench, earth pressure, box culvert, soil arching, centrifuge testing, high embankments. Deux ponceaux rectangulaires coules sur place et renforces (ponceaux Longs Creek et McBean Brook), qui ont une geometrie similaire, ont ete instrumentes afin de mesurer les pressions des terres. La structure Longs Creek est un ponceau rectangulaire a double cellule de 7,30 m de largeur par 4,53 m de hauteur, place sous 14,10 m de remblai, et construit a l'aide de la methode d'installation par projection positive (IPP). La structure McBean est un ponceau rectangulaire a double cellule de 6,75 m de largeur par 4,65 m de hauteur, place sous 25,10 m de remblai, construit avec la methode d'installation de tranchee induite (ITI). Les pressions des terres sont suivies depuis que la hauteur du remblai sur le ponceau a ete augmentee pour les deux structures. Les donnees du ponceau McBean Brook a une hauteur de remblai de 14,40 m sont comparees aux donnees du ponceau Longs Creek. La geometrie similaire de ces deux prototypes de ponceaux offre une opportunite unique de comparer les performances selon les differentes methodes d'installation. Pour une hauteur de remblai comparable, les pressions des terres verticales mesurees sur les toits etaient de 0,94 et 0,56 fois les pressions des terres pour le ponceau Longs Creek (IPP) et le ponceau McBean Brook (ITI), respectivement. La pression des terres laterale moyenne etait de 0,32 fois la pression des terres au ponceau Longs Creek (IPP), et 0,46 fois la pression des terres au ponceau McBean Brook (ITI). Les donnees du ponceau McBean Brook en lien avec la pression de contact a la base sont aussi presentees mais n'ont pas pu etre comparees directement avec le ponceau Longs Creek, puisque les pressions a la base n'y ont pas ete mesurees. Les pressions mesurees a la base du ponceau McBean Brook demontrent la presence de forces de trainee developpees sur les murs de cote des ponceaux rectangulaires. Des resultats obtenus a partir d'essais en centrifuge sont aussi presentes et compares aux mesures de pression sur le terrain. Mots-cles : tranchee induite, pression des terres, ponceau rectangulaire, effet d'arche, essai en centrifuge, digues elevees., Introduction Modern highway construction and development sometimes requires construction of high embankments (fill height above the culvert top, H ≥ 10 m) over underground rigid and flexible structures. The high [...]

Earth pressure data from the field instrumentation of a cast-in-place reinforced rectangular box culvert are presented in this paper. The instrumented culvert is a 2.60 m by 3.60 m double-cell reinforced cast-in-place rectangular box buried under 25.10 m of fill constructed using the induced trench installation (ITI) method. The average earth pressure measured across the roof was 0.42 times the overburden pressure, and an average of 0.52 times the overburden pressure was measured at mid-height of the culvert on the sidewalls. Base contact pressure under the rectangular box culvert was also measured, providing field-based data demonstrating increased base pressure resulting from downward drag forces developed along the sidewalls of the box culvert. An average increase of 25% from the measured vertical earth pressures on the roof plus the culvert dead load (DL) pressure was calculated at the culvert base. A model culvert was also tested in a geotechnical centrifuge to obtain data on earth pressures at the top, sides, and base of the culvert. The data from the centrifuge testing were compared with the prototype structure, and the centrifuge test results agreed closely with the measured field prototype pressures, in spite of the fact that full similitude was not attempted in centrifuge testing. Key words: induced trench, earth pressure, box culvert, soil arching, centrifuge testing, high embankments. Cet article presente des donnees de pressions des terres provenant d'instrumentation sur le terrain d'un ponceau rectangulaire renforce et coule en place. Le ponceau instrumente est un ponceau rectangulaire renforce a double cellule de 2,60 m par 3,60 m, coule en place sous 25,10 m de remblai, et construit avec la methode d'installation de tranchee induite (ITI). La pression des terres moyenne sur la paroi superieure etait de 0,42 fois la pression des terres, et une moyenne de 0,52 fois la pression des terres etait mesuree a la mi-hauteur des murs du ponceau. La pression de contact a la base sous le ponceau rectangulaire a aussi ete mesuree, ce qui permet de demontrer a l'aide de resultats de terrain qu'une augmentation de la pression a la base est causee par les forces de trainee vers le bas developpees le long des murs des cotes du ponceau rectangulaire. Une augmentation moyenne de 25 % de la pression des terres verticale mesuree sur la paroi superieure, en plus de la pression de charge morte du ponceau, a ete calculee a la base du ponceau. Un ponceau modele a aussi ete teste dans une centrifuge geotechnique afin d'obtenir des donnees sur les pressions des terres au haut, sur les cotes, et a la base du ponceau. Les donnees des essais en centrifuge ont ete compares avec la structure prototype, et les resultats d'essais en centrifuge correspondent bien avec les mesures de pressions sur le prototype de terrain, malgre que les essais en centrifuge ne tentaient pas d'etre totalement similaires au terrain. Mots-cles : tranchee induite, pression des terres, ponceau rectangulaire, effet d'arche, essai en centrifuge, digues elevees. [Traduit par la Redaction], Introduction Routing and construction of modern highways often require high embankment fills (fill height above culvert top, H ≥ 10 m) crossing over underground rigid and flexible culverts, thereby resulting [...]

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 [...]

The active earth pressure used in the design of gravity walls is calculated based on the internal friction angle of the retained soil or backfill. However, the friction angle of a soil changes during the deformation process. For drained loading, the mobilized friction angle varies between the peak and critical-state friction angles, depending on the level of shear strain in the retained soil. Consequently, there is not a single value of friction angle for the retained soil mass, and the active earth pressure coefficient changes as the wall moves away from the backfill and plastic shear strains in the backfill increase. In this paper, the finite element method is used to study the evolution of the active earth pressure behind a gravity retaining wall, as well as the shear patterns developing in the backfill and foundation soil. The analyses relied on use of a two-surface plasticity constitutive model for sands, which is based on critical-state soil mechanics. Key words: finite elements, plasticity, retaining walls, sands. La pression active des terres utilisee dans la conception des murs gravitaires est calculee a partir de l'angle de friction interne du sol ou du remblai retenu. Cependant, l'angle de friction d'un sol change durant le processus de deformation. Dans le cas d'un chargement draine, l'angle de friction mobilise varie entre l'angle de friction au pic et celui a l'etat critique, dependant du niveau de deformation en cisaillement dans le sol retenu. En consequence, il n'y a pas de valeur unique d' angle de friction pour une masse de sol retenue, et le coefficient de pression active des terres varie a mesure que le mur se separe du remblai et que les deformations plastiques en cisaillement augmentent dans le remblai. Dans cet article, la methode par elements finis est utilisee pour etudier l'evolution de la pression active des terres derriere un mur de soutenement gravitaire, ainsi que les patrons de cisaillement qui se developpent dans le remblai et dans le sol de fondation. Les analyses sont realisees a l' aide d' un modele constitutif de plasticite a deux surfaces pour des sables, qui est base sur la mecanique de l' etat critique des sols. Mots-cles : elements finis, plasticite, murs de soutenement, sables. [Traduit par la Redaction], Introduction The active earth pressure acting on the back of a retaining wall controls its design. The active earth pressure is expressed as the product of the vertical effective stress [...]

A novel pressure sensing scheme based on the effect of a conforming elastomer material on the transmission spectrum of tilted fiber Bragg gratings is presented. Lateral pressure on the elastomer increases its contact angle around the circumference of the fiber and strongly perturbs the optical transmission of the grating. Using an elastomer with a Young's modulus of 20 MPa, a Poisson ratio of 0.48, and a refractive index of 1.42, the sensor reacts monotonically to pressures from 0 to 50 kPa (and linearly from 0 to 15 kPa), with a standard deviation of 0.25 kPa and maximum error of 0.5 kPa. The data are extracted from the optical transmission spectrum using Fourier analysis and we show that this technique makes the response of the sensor independent of temperature, with a maximum error of 2% between 25[degrees]C and 75[degrees]C. Finally, other pressure ranges can be reached by using conforming materials with different modulii or applying the pressure at different orientations. [c] 2010 Optical Society of America OCIS codes: 060.2340, 060.2370, 050.2770.

Passive earth pressure is recorded in two different tests, using a 6.7-m long, 2.9-m wide soil container. In these tests, sand with 7% silt content is densely compacted behind a moveable test wall to a supported height of 1.68 m (5.5 ft). Lateral load is applied to the vertical reinforced concrete wall section, which displaces freely along with the adjacent backfill in the horizontal and vertical directions. The recorded passive resistance is found to increase until a peak is reached at a horizontal displacement of 2.7-3% of the supported backfill height, decreasing thereafter to a residual level. In this test configuration, a triangular failure wedge shape is observed, due to the low mobilized wall-soil friction. Backfill strength parameters are estimated based on this observed failure mechanism. From these estimates, along with triaxial and direct shear test data, theoretical predictions are compared with the measured passive resistance. Using the test data, a calibrated finite-element model is employed to produce additional load-displacement curves for a wider range of practical applications (e.g., potential bridge deck displacement during a strong earthquake). Hyperbolic model approximations of the load-displacement curves are also provided. DOI: 10.1061/(ASCE)GT.1943-5606.0000386 CE Database subject headings: Passive pressure; Earth pressure; Retaining walls; Full-scale tests; Soil-structure interactions; Load factors; Simulation; Displacement. Author keywords: Passive pressure; Retaining wall: Large-scale tests; Soil-structure interaction.

A new diagnostic technique for measurements of temperature and pressure distribution in gaseous flows has been developed. The technique, based on infrared planar laser-induced fluorescence (IR-PLIF), is applicable to all IR-active species. A simple two-line excitation approach is used for measurements of temperature, while pressure measurements utilize online excitation on one rotational line and offline excitation on another. A demonstration of the technique in a supersonic underexpanded jet of 30% C[O.sub.2] and 70% [N.sub.2] was performed, and the results are, to the best of our knowledge, the first demonstration of temperature and pressure imaging using IR-PLIF. The developed diagnostic shows potential for single-shot two-dimensional measurements of temperature and pressure in gaseous flows. [c] 2010 Optical Society of America OCIS codes: 110.3080, 120.5475, 120.6780.

Full explanation for the pathogenesis of syringomyelia (SM), a neuropathology characterized by the formation of a cystic cavity (syrinx) in the spinal cord (SC), has not yet been provided. It has been hypothesized that abnormal cerebrospinal fluid (CSF) pressure, caused by subarachnoid space (SAS) flow blockage (stenosis), is an underlying cause of syrinx formation and subsequent pain in the patient. However, paucity in detailed in vivo pressure data has made theoretical explanations for the syrinx difficult to reconcile. In order to understand the complex pressure environment, four simplified in vitro models were constructed to have anatomical similarities with post-traumatic SM and Chiari malformation related SM. Experimental geometry and properties were based on in vivo data and incorporated pertinent elements such as a realistic CSF flow waveform, spinal stenosis, syrinx, fexible SC, and flexible spinal column. The presence of a spinal stenosis in the SAS caused peak-to-peak cerebrospinal fluid CSF pressure fluctuations to increase rostral to the stenosis. Pressure with both stenosis and syrinx present was complex. Overall, the interaction of the syrinx and stenosis resulted in a diastolic valve mechanism and rostral tensioning of the SC. In all experiments, the blockage was shown to increase and dissociate SAS pressure, while the axial pressure distribution in the syrinx remained uniform. These results highlight the importance of the properties of the SC and spinal SAS, such as compliance and permeability, and provide data for comparison with computational models. Further research examining the influence of stenosis size and location, and the importance of tissue properties, is warranted. [DOI: 10.1115/1.4000089] Keywords: cerebrospinal fluid hydrodynamics, syringomyelia, Chiari malformation, hydrocephalus, fluid-structure interaction, spinal cord, subarachnoid space stenosis, syrinx, intracranial and spinal pressures, in vitro model

The National Institute of Standards and Technology (NIST) has redefined its gas pressure scale, up to 17 MPa, based on two primary standard piston gauges. The primary standard piston gauges [...]

The statistics of pressure fluctuations above and within three types of porous granular beds such as in gravel bed streams, rivers, and man-made canals are investigated by data gained via laboratory flume experiments. The flow conditions examined include a diversity of hydrodynamic loads that increase up to the point where single grains are moving from time to time, without causing severe modification to the bed texture and the related positions of the pressure sensors. Analysis is performed by means of histograms and spectral techniques and vertical intensity profiles. Two simplified equations are found that describe the vertical decrease for the standard deviation of the measured fluctuations indicating drag and lift, respectively, nondimensionalized by the mean bed shear stress. The former fluctuation is described by a crude linear fit, whereas the latter clearly shows that the lift intensity decreases exponentially in the porous bed with a decay distance of one to two times the equivalent grain roughness. Within the subsurface layer the standard deviation reaches a nonzero constant, mainly dominated by long-wave pressure fields that are convected in the outer flow. These findings can be used in future sediment transport models that use force balance approaches to determine incipient motion conditions. DOI: 10.1061/(ASCE)HY.1943-7900.0000251 CE Database subject headings: Open channel flow; Gravel; Turbulence; Power spectral density; Laboratory tests; River beds. Author keywords: Open-channel flow; Gravel bed; Turbulence; Pressure fluctuation; Spectral density; Interstitial.

The dynamics of unstart in a floor-mounted inlet-isolator model in a Mach 5 flow are investigated experimentally using particle image velocimetry and fast-response wall pressure measurements. The inlet compression is obtained with a 6-deg ramp and the isolator is a rectangular straight duct that is 25.4 mm high by 50.8 mm wide by 242.3 mm long. Unstart is initiated from the scram jet mode (fully supersonic in the isolator) by deflecting a motorized flap at the downstream end of the isolator. With the flap fully down, the particle image velocimetry data of the started flow capture the characteristics of the isolator boundary layers and the initial inlet reflected shock system. During unstart, the unstart shock system propagates upstream through the inlet-isolator. The particle image velocimetry data reveal a complex, three-dimensional flow structure that is strongly dependent on viscous mechanisms. Particularly, the unstart shock system propagates upstream and induces significant boundary-layer separation. Side-view particle image velocimetry data show that the locations of strongest separation during unstart correlate with the impingement locations of the initial inlet shock as it reflects down the isolator. For example, in the middle of unstart, the unstart shock system is associated with massive separation of the ceiling boundary layer that begins where the first inlet shock reflection impinges on the ceiling. The observation that separation increases at the inlet shock reflection impingement locations is likely due to the fact that the boundary layers in these locations are subject to larger adverse pressure gradients, thus making them more susceptible to separation. During the unstart process, large regions of separated flow form near the floor and ceiling with reverse flow velocities up to about 0.4[U.sub.[infinity]]. These regions of separated, subsonic flow appear to extend to the isolator exit, creating a path by which the isolator exit boundary condition can be communicated upstream. Plan-view particle image velocimetry data show the unstart process begins with separation of the isolator sidewall boundary layers. Overall, the unstart flow structure is highly three-dimensional. DOI: 10.2514/1.J050037

An infinite-line probe is commonly used to measure unsteady pressure in high-temperature environments while protecting the pressure transducer. In this study, an existing theoretical model is used to derive the response of a waveguide pressure measuring system. An ambient temperature centrifugal compressor rig acts as an experimental source of fluctuating pressure. The compressor is operated at different discrete rotational speeds, and the blade-passing frequencies are used to obtain frequency response data. In the experiments, pressure waves attenuated at a rate faster than that predicted by the theoretical model for a 0.322 m (12 in.) sensor offset. Furthermore, the decay in the magnitude of the pressure oscillations accelerated at blade-passing frequencies above 9 kHz. A unique contribution of this study is to show that whereas the experimentally observed overall attenuation is broadly consistent with the theoretical predictions, pressure oscillations corresponding to individual blade passages may be disproportionally attenuated. [DOI: 10.1115/1.3159387]

The hydrant pressure head in an on-demand water distribution system can be subject to high fluctuation depending on the discharge flowing inside the pipes, with consequent impacts on the performance of on-farm irrigation systems. In this work, an Italian water distribution system was analyzed using the AKLA model at upstream discharges of 1,200 and 600 L x [s.sup.-1] to estimate the range of hydrant pressure variation. A computer model was developed, calibrated, and used to evaluate the performance of a drip irrigation system by relating the on-farm network with the hydrant characteristic curve at a certain operating status. The flow regulator within the hydrant played an important role in stabilizing the performance of the network at hydrant pressures higher than 27 m. At lower hydrant pressures, to apply the same amount of water, irrigation time must be extended by 17 and 95% for pressure heads of 20 and 12 m, respectively. These approaches described have great utility to ensure adequate irrigation management when water is delivered by pressurized on-demand systems. DOI: 10.1061/(ASCE)IR.1943-4774.0000170 CE Database subject headings: Network analysis; Hydraulic networks; Hydraulic pressure; Trickle irrigation; Water flow; Water distribution systems. Author keywords: Network characteristic curve; Hydrant pressure variation; Irrigation performance; Network analysis; Flow regulator.

Author(s): Kresimir Kumericki [sup.1] Author Affiliations: (1) Department of Physics, Faculty of Science, University of Zagreb, Zagreb, Croatia ARISING FROM V. D. Burkert et al. Nature 10.1038/s41586-018-0060-z (2018) Understanding the [...]

Although uplift motion of flat-bottom cylindrical shell tanks has been considered to contribute toward various damages to the tanks, the mechanics were not fully understood. As well as uplift displacement of the tanks, fluid pressure accompanying the uplift motion of the tanks may play an important role in the cause of the damage. An accurate estimate of the fluid pressure induced by the uplift motion of the tanks is indispensable in protecting the tanks against destructive earthquakes. As a first step of a series of research, this study mathematically derives the fluid pressure on a rigid rectangular tank with a unit depth accompanying angular acceleration, which acts on a pivoting bottom edge. The rectangular tank employed herein is equivalent to a thin slice of the central vertical cross section of a rigid flat-bottom cylindrical shell tank. Assuming a perfect fluid and velocity potential, a continuity equation is given by the Laplace equation in Cartesian coordinates. The fluid velocities accompanying the motions of the walls and bottom plate constitute the boundary conditions. Since this problem is set as a parabolic partial differential equation of the Neumann problem, the velocity potential is solved with the Fourier-cosine expansion. The derivative of the velocity potential with respect to time gives the fluid pressure at an arbitrary point inside the tank. A mathematical solution for evaluating the fluid pressure accompanying the angular acceleration acting on the pivoting bottom edge of the tank is given by an explicit function of a dimensional variable of the tank, but with the Fourier series. The proposed mathematical solution well converges with a few first terms of the Fourier series. Values of the fluid pressure computed by the explicit finite element (FE) analysis well agrees with those by the proposed mathematical solution. For the designers' convenience, diagrams that depict the fluid pressures normalized by the maximum tangential acceleration given by the product of the angular acceleration and diagonals of the tank are also presented. Consequently, the mathematical solution given by the Fourier series converges easily and provides accurate evaluation of the fluid pressures on a rigid rectangular tank accompanying the angular acceleration acting on the pivoting bottom edge. Irregularity in the fluid pressure distribution increases as the tank becomes taller. [DOI: 10.1115/1.4000546] Keywords: flat-bottom cylindrical shell tank, fluid pressure, angular acceleration, uplift motion, Fourier-cosine expansion, velocity potential, normalized fluid pressure, rigid rectangular tank

To protect flat-bottom cylindrical tanks against severe damage from uplift motion, accurate evaluation of accompanying fluid pressures is indispensable. This paper presents a mathematical solution for evaluating the fluid pressure on a rigid flat-bottom cylindrical tank in the same manner as the procedure outlined and discussed previously by the authors (Taniguchi, T., and Ando, Y., 2010, 'Fluid Pressures on Unanchored Rigid Rectangular Tanks Under Action of Uplifting Acceleration,' ASME J. Pressure Vessel Technol., 132(1), p. 011801). With perfect fluid and velocity potential assumed, the Laplace equation in cylindrical coordinates gives a continuity equation, while fluid velocity imparted by the displacement (and its time derivatives) of the shell and bottom plate of the tank defines boundary conditions. The velocity potential is solved with the Fourier--Bessel expansion, and its derivative, with respect to time, gives the fluid pressure at an arbitrary point inside the tank. In practice, designers have to calculate the fluid pressure on the tank whose perimeter of the bottom plate lifts off the ground like a crescent in plan view. However, the asymmetric boundary condition given by the fluid velocity imparted by the deformation of the crescent-like uplift region at the bottom cannot be expressed properly in cylindrical coordinates. This paper examines applicability of a slice model which is a rigid rectangular tank with a unit depth vertically sliced out of a rigid flat-bottom cylindrical tank with a certain deviation from (in parallel to) the center line of the tank. A mathematical solution for evaluating the fluid pressure on a rigid flat-bottom cylindrical tank accompanying the angular acceleration acting on the pivoting bottom edge of the tank is given by an explicit function of a dimensional variable of the tank, but with Fourier series. It well converges with a few first terms of the Fourier series and accurately calculates the values of the fluid pressure on the tank. In addition, the slice model approximates well the values of the fluid pressure on the shell of a rigid flat-bottom cylindrical tank for any points deviated from the center line. For the designers' convenience, diagrams that depict the fluid pressures normalized by the maximum tangential acceleration given by the product of the angular acceleration and diagonals of the tank are also presented. The proposed mathematical and graphical methods are cost effective and aid in the design of the flat-bottom cylindrical tanks that allow the uplifting of the bottom plate. [DOI: 10.1115/1.4000374] Keywords: flat-bottom cylindrical tank, fluid pressure, uplift motion, Fourier--Bessel expansion, velocity potential pivoting edge, normalized fluid pressure, angular acceleration, slice model

This paper presents new results for numerical predictions of air flow and pressure distribution in two commonly used elbows: (1) 90[degrees] mitered duct elbows with turning vanes having 0.05 m radius, 0.038 m vane spacing and (2) 90[degrees] mitered duct elbows without turning vanes, in 0.2 x 0.2 m (8 in. X 8 in.) duct cross section using the STAR-CD computational fluid dynamics (CFD) code. A k-[epsilon] turbulence model for high Reynolds number and k-[epsilon] Chen model were used for that purpose for comparative purposes. The simulation used 13 different Reynolds numbers chosen between the range of 1 X [10.sup.5] and 2 x [10.sup.6]. To validate the CFD results, the results of two experimental papers using guided vanes were compared with simulated vane runs under the same condition. The first experimental study used a 0.6 x 0.6 m (24 in. X 24 in.) square elbow with 0.05 m radius, 0.038 m vane spacing and air velocities at 2.54 m/s (500 fpm) and 25.4 m/s (5,000 fpm), the second experiment used a 0.81 X 0.2 m (32 in. X 8 in.) rectangular elbow geometry with 0.05 m radius, 0.038 m vane spacing with air velocities from 10.16 m/s (2,000 fpm) to 13.97 m/s (2,750 fpm). For Reynolds numbers (1.00-2.00) x [10.sup.5] the pressure drop difference between vaned and unvaned elbows was found to be 35 Pa as compared to 145 Pa. The simulations also agreed reasonably well with published experimental results. For the 0.6X0.6 m (24 in. x 24 in.) square elbow and 0.81 X 0.2 m (32 in. X 8 in.) rectangular elbow with vanes, the difference in pressure drop was 3.9 and 4.1% respectively and indicates that CFD models can be used for predictive purposes in this important HVAC applications area. DOI: 10.1061/(ASCE)0733-9402(2009)135:4(119) CE Database subject headings: Flow simulation; Velocity profile; Predictions; Air flow.

This paper presents 9 years of measured pore pressures from eight piezometers installed in a marine clay slope in southeast Norway and the results of a two-dimensional finite element (FE) analysis performed to evaluate infiltration effects on groundwater flow and pore-pressure response. The assumed time-varying boundary flux record used in the analysis to simulate infiltration considers the effects of temperature, snow depth, land-use practices, and soil hydraulic conductivity. The pore-pressure records and analyses show that: (i) the maximum pore pressure reached is nearly the same each year; (ii) this maximum corresponds to a groundwater surface at or near the ground surface; (iii) the two-dimensional groundwater model used for the analysis is adequate for understanding of factors affecting infiltration, seepage patterns, and pore-pressure variations; and (iv) it is difficult to precisely model all aspects of the observed pore-pressure variations. Key words: marine clay, quick clay, landslide, slope stability, precipitation, pore-pressure measurements. L'article presente des resultats de 9 ans de mesures de pression interstitielle prises sur huit piezometres installes dans une pente d'argile marine au sud-est de la Norvege et les resultats d'une analyse par elements finis en deux dimensions effectuee pour evaluer les effets de l'infiltration sur l'ecoulement de l'eau souterraine et sur les pressions interstitielles. Les estimations utilisees comme frontiere de flux variable selon le temps qui ont servi dans l'analyse pour simuler l'infiltration considerent les effets de la temperature, de la profondeur de la neige, des utilisations du territoire et de la conductivite hydraulique du sol. Les donnees de pressions interstitielles et les analyses montrent que : La pression interstitielle maximale est a peu pres la meme chaque annee; Ce maximum correspond a une nappe phreatique a la surface ou pres de la surface; Le modele a deux dimensions utilise pour l'analyse de l'eau souterraine est adequat pour comprendre les facteurs qui affectent l'infiltration, les exfiltrations et les variations de pressions interstitielles; Il est difficile de modeliser avec precision tous les aspects des variations de pressions interstitielles observees. Mots-cles : argile marine, argile sensible, glissement de terrain, stabilite de pente, precipitations, mesures de pression interstitielle. [Traduit par la Redaction], Introduction From October 1969 to August 1978, data was recorded for eight piezometers installed in marine clay slopes at a study site at the Lodding farm in the Romerike district [...]

A detailed review and analysis of the hydrodynamic characteristics of laminar developing and fully developed flows in noncircular ducts is presented. New models are proposed, which simplify the prediction of the friction factor--Reynolds product f Re for developing and fully developed flows in most noncircular duct geometries found in heat exchanger applications. By means of scaling analysis it is shown that complete problem may be easily analyzed by combining the asymptotic results for the short and long ducts. Through the introduction of a new characteristic length scale, the square root of cross-sectional area, the effect of duct shape has been minimized. The new model has an accuracy of [+ or -]10% or better for most common duct shapes when nominal aspect ratios are used, and [+ or -]3% or better when effective aspect ratios are used. Both singly and doubly connected ducts are considered. [DOI: 10.1115/1.4000377] Keywords: laminar flow, noncircular ducts, hydrodynamic entrance length, developing flow, modeling, pressure drop

This study assessed the effects of meal volume (MV) and calorie load (CL) on gastric function. MRI and a minimally invasive fiber-optic recording system (FORS) provided simultaneous measurement of gastric volume and pressure changes during gastric tilting and emptying of a liquid nutrient meal in physiological conditions. The gastric response to 12 iso-osmolar MV-CL combinations of a multinutrient drink (MV: 200, 400, 600, 800 ml; CL: 200, 300, 400 kcal) was tested in 16 healthy subjects according to a factorial design. Total gastric volume (TGV) and gastric content volume (GCV = MV + secretion) were measured by MRI during nasogastric meal infusion and gastric emptying over 60 min. Intragastric pressure was assessed at 1 Hz by FORS. The dynamic change in postprandial gastric volumes was described by a validated three-component linear exponential model. The stomach expanded with MV, but the ratio of GCV:MV at [t.sub.0] diminished with increasing MV (P < 0.01). Postprandial changes in TGV followed those of GCV. Intragastric pressure increased with MV, and this effect was augmented further by CL (P = 0.02); however, the absolute pressure rise was gastric accommodation; gastric emptying; intragastric pressure doi: 10.1152/ajpgi.00117.2009.

This paper discussed the computational accuracy of roughsurface point-contact isothermal elastohydrodynamic lubrication (EHL) analysis by investigating the effects of differential scheme, viscosity-pressure, and shear-thinning models. An EHL experiment with multitransverse ridges was employed as simulated target. Four differential schemes, including the combined and the separate first-order and second-order backward schemes, were investigated. It is found that the separate second-order backward scheme offers the best results based on the comparison with the experimental data, with which two roughness derivatives may be fully or partially canceled each other; thus, the discretization error induced by roughness can be reduced. The consistency of differential schemes is an important issue for the separate schemes. The Yasutomi free-volume viscosity-pressure model and the Eyring rheological model are found to yield the numerical simulations the closest to experimental results. [DOI: 10.1115/1.2842245] Keywords: EHL, differential schemes, viscosity-pressure models, rheological models

Contours of surface texture of contact faces are not always parallel to the directions of the axis in solving Reynolds equations with finite difference method, and this often induces significant pressure saw-tooth effect, which results in an unignored analysis error. In this paper, pseudo-nine-point finite difference, as a new finite difference method, is introduced to solve the lubrication numerical problem of pressure saw-tooth. Also, application is carried out in gas lubrication of hard disk systems to verify the validity of the new method. In analysis, pressure distributions and gas floating forces are calculated for two different types of sliders, and the astringency and efficiency of the new method is discussed. Numerical results show that the pseudo-nine-point finite difference method can restrain pressure saw-tooth evidently, and presents better astringency and efficiency than the traditional five-point finite difference method. With the increase in mesh density, pressure distribution and gas floating force trend to steady. Also, numerical values of the floating force agree well with the experimental ones. [DOI: 10.1115/1.3195039] Keywords: pseudo-nine-point finite difference, pressure saw-tooth, gas lubrication

Experimental pitot pressure measurements in impulse facilities have typically had large-scale harmonic fluctuations associated with them. A combined experimental and numerical approach is used to investigate if a Helmholtz resonance is created from the shrouding that protects the pressure sensor from particle impact, rather than from disturbances being present in the freestream. To verify this experimentally, hydraulic oil was used to change the sound speed in the cavity. Numerical calculations of the pitot probe were used to show that both the steady and the expected transient inflow cause a Helmholtz resonance of similar period. However, a 5 % isothermal level of freestream noise was required to match the experimental fluctuation levels. Viscous effects were also shown to be significant during the initial transient response of the pressure measurement. A new pitot probe design was successfully tested and shown to be able to reduce the magnitude and period of the fluctuations. DOI: 10.2514/1.42543

A real-time estimation of water distribution system state variables such as nodal pressures and chlorine concentrations can lead to savings in time and money and provide better customer service. While a good knowledge of nodal demands is prerequisite for pressure and water quality prediction, little effort has been placed in real-time demand estimation. This study presents a real-time demand estimation method using field measurement provided by supervisory control and data acquisition systems. For real-time demand estimation, a recursive state estimator based on weighted least-squares scheme and Kalman filter are applied. Furthermore, based on estimated demands, real-time nodal pressures and chlorine concentrations are predicted. The uncertainties in demand estimates and predicted state variables are quantified in terms of confidence limits. The approximate methods such as first-order second-moment analysis and Latin hypercube sampling are used for uncertainty quantification and verified by Monte Carlo simulation. Application to a real network with synthetically generated data gives good demand estimations and reliable predictions of nodal pressure and chlorine concentration. Alternative measurement data sets are compared to assess the value of measurement types for demand estimation. With the defined measurement error magnitudes, pipe flow data are significantly more important than pressure head measurements in estimating demands with a high degree of confidence. DOI: 10.1061/(ASCE)HY.1943-7900.0000086 CE Database subject headings: Estimation; Least squares method; Water distribution systems; Uncertainty principles; Limit analysis.

The performance of rigid surface structures such as concrete pavements and slabs-on-grade supported by a deteriorated subgrade and experiencing local contact loss is investigated experimentally and numerically in this study. A laboratory setup has been designed to facilitate the simulation of subsurface erosion and measure the changes in contact pressure at selected locations under a slab-on-grade supported on granular material. The presence of erosion voids under a slab-on-grade can lead to rapid increase in the contact pressure in the immediate vicinity of the void in addition to an increase in tensile stresses at the outermost fibers of the slab. This preliminary study suggests that efforts to detect and arrest the growth of erosion voids under slabs-on-grade should be made before the voids reach the size where significant loss of support develops and the tensile strength of the slab material is exceeded. DOI: 10.1061/(ASCE)GT.1943-5606.0000097 CE Database subject headings: Slabs; Soil erosion; Deterioration; Voids; Subgrades; Underground structures.