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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 [...]

The establishment of correlations between the small-strain shear modulus ([G.sub.o]) and other soil parameters (such as the oedometer constrained modulus, [M.sub.oedo]) at large deformations constitutes an important step toward more precise modeling of soil deformation behavior. In this study, the shear wave velocities ([V.sub.s]) of 22 different granular soils of various physical characteristics were measured experimentally using the piezoelectric ring-actuator technique (P-RAT) incorporated in the conventional oedometer cell. For each sample tested, the development of [M.sub.oedo] with the development of relative density ([I.sub.d]), as well as the void ratio (e), was recorded. Then, the obtained [V.sub.s] and [M.sub.oedo]/[G.sub.o] trends were correlated to the physical parameters of the tested granular soils with the development of e and [I.sub.d]. A practical application employing the achievements in geotechnical engineering design was also evaluated. Based on the proposed correlations, geotechnical designers can easily estimate in situ stress-settlement behavior from the predicted [M.sub.oedo] and [I.sub.d] values using simple in situ measurements. Key words: piezoelectric ring-actuator technique (P-RAT), shear wave velocity, shear modulus, deformation modulus, improved correlations. L'etablissement de correlations entre le module de cisaillement des petites deformations ([G.sub.o]) et d'autres parametres du sol (tels que le module contraint de l'oedometre, [M.sub.oedo]) pour les grandes deformations constitue une etape importante vers une modelisation plus precise du comportement des sols en deformation. Dans cette etude, les vitesses des ondes de cisaillement ([V.sub.s]) de 22 sols granulaires differents ayant des caracteristiques physiques variees ont ete mesurees experimentalement en utilisant la technique de l'actionneur annulaire piezoelectrique (P-RAT) incorporee dans la cellule oedometrique classique. Pour chaque echantillon teste, le developpement de [M.sub.oedo] avec le developpement de la densite relative ([I.sub.d]), ainsi que l'indice des vides (e), a ete enregistre. Ensuite, les tendances [V.sub.s] et [M.sub.oedo]/[G.sub.o] obtenues ont ete correlees aux parametres physiques des sols granulaires testes avec le developpement de e et [I.sub.d]. Une application pratique utilisant les resultats obtenus dans la conception d'ingenierie geotechnique a egalement ete evaluee. Sur la base des correlations proposees, les concepteurs geotechniques peuvent facilement estimer le comportement in situ contrainte-tassement a partir des valeurs predites de [M.sub.oedo] et [I.sub.d] en utilisant de simples mesures in situ. Mots-cles: technique de l'actionneur annulaire piezoelectrique (P-RAT), vitesse des ondes de cisaillement, module de cisaillement, module de deformation, correlations ameliorees., 1. Introduction Small- and large-strain soil parameters, which are generally referred to as short- and long-term soil parameters, respectively, are key factors in geotechnical designs. Researchers customarily afford significant attention [...]

Determining shear wave velocity is a critical technique in bender element tests, as it can be readily affected by near-field effects, wave reflection, and other factors. This study proposes a new method based on the dyadic wavelet transform modulus maxima. Combining the local modulus maxima of dyadic wavelet transform approximate coefficients at fine decomposition levels and an appropriate threshold value, the proposed method can automatically detect the target point. For validation, a comparative study among the dyadic wavelet transform modulus maxima, peak-to-peak, first arrival, and cross-correlation methods was carried out using 140 sets of bender element signals. The comparison results show that the proposed method not only mitigates the adverse effects of near-field, later major peaks, and noise contamination, but is also more robust in estimating shear wave velocity. Key words: small-strain shear modulus, bender element test, shear wave velocity, dyadic wavelet transform, travel time, de-noising. La determination de la vitesse des ondes de cisaillement est une technique essentielle dans les essais d'elements de flexion, car elle peut etre facilement affectee par les effets de champ proche, la reflexion des ondes et d'autres facteurs. Cette etude propose une nouvelle methode basee sur le module maximal de la transformee dyadique en ondelettes. En combinant les modules maximaux locaux des coefficients approximatifs de la transformee dyadique en ondelettes a des niveaux de decomposition fine et une valeur seuil appropriee, la methode proposee peut detecter automatiquement le point cible. Pour la validation, une etude comparative entre les methodes du module maximal de la transformee dyadique en ondelettes, du pic a pic, de la premiere arrivee et de la correlation croisee a ete realisee en utilisant 140 ensembles de signaux d'elements de courbure. Les resultats de la comparaison montrent que la methode proposee permet non seulement d'attenuer les effets nefastes de la contamination en champ proche, des pics majeurs ulterieurs et du bruit, mais aussi d'etre plus robuste dans l'estimation de la vitesse des ondes de cisaillement. Mots-cles : module de cisaillement a faible deformation, test de l'element cintreur, vitesse des ondes de cisaillement, transformee en ondelettes dyadiques, duree du voyage, debruitage., Introduction Shear wave velocity is a critical index in calculating small-strain shear modulus via bender element tests. Currently, common shear wave velocity estimation methods include first arrival (Lee and Santamarina [...]

Random field theory is widely used to model spatial variability of soil properties. However, random field modeling focuses mainly on the estimate of spatial correlation structure. The dependence structure that is necessary to construct the joint probability distribution over a random field is usually not characterized. The aim of this research is twofold. First, this paper focuses on characterizing the dependence structure underlying a random field based on cone penetration test (CPT) data. The copula approach is adopted to represent dependencies and the best-fit dependence (copulas) are identified from the CPT data. It is found that the nonGaussian dependencies can be a real phenomenon in spatial fluctuation of the soil shear strength parameter. Second, this paper provides formulations for generating random fields with Gaussian or nonGaussian dependencies, and investigates whether the improper use of the dependence structure could lead to significant bias in failure probability. The generated one-dimensional (1-D) and two-dimensional (2-D) random fields of a cohesive slope under different dependencies are compared. Large deviation in probabilistic results implies that the effect of dependencies on failure probability can be nontrivial. Therefore, the complete random field characterization should involve the estimate of both correlation structure and dependence structure. Key words: random field, spatial variability, dependence structure, copulas, geotechnical reliability. La theorie des champs aleatoires est largement utilisee pour modeliser la variabilite spatiale des proprietes du sol. Cependant, la modelisation de champs aleatoires se concentre principalement sur l'estimation de la structure de correlation spatiale. La structure de dependance necessaire pour construire la distribution de probabilite conjointe sur un champ aleatoire n'est generalement pas caracterisee. Le but de cette recherche est double. Tout d'abord, cet article se concentre sur la caracterisation de la structure de dependance sous-jacente a un champ aleatoire base sur des donnees de tests de penetration au cone (CPT). L'approche de la copule est adoptee pour representer les dependances et la meilleure dependance d'ajustement (copules) est identifiee a partir des donnees du CPT. On trouve que les dependances non-gaussiennes peuvent etre un phenomene reel dans la fluctuation spatiale du parametre de resistance au cisaillement du sol. Deuxiemement, cet article fournit des formulations pour generer des champs aleatoires avec des dependances gaussiennes ou non-gaussiennes, et etudie si l'utilisation inappropriee de la structure de dependance pourrait conduire a un biais significatif dans la probabilite de defaillance. Les champs aleatoires unidimensionnelles (1D) et bidimensionnelles (2D) generes d'une pente cohesive sous differentes dependances sont compares. Un grand ecart dans les resultats probabilistes impliquait que l'effet des dependances sur la probabilite de defaillance pouvait etre non trivial. Par consequent, la caracterisation complete du champ aleatoire devrait impliquer l'estimation de la structure de correlation et de la structure de dependance. Mots-cles : champ aleatoire, variabilite spatiale, structure de dependance, copules, fiabilite geotechnique., Introduction Spatial variability is widely observed in soil properties (Low 2014). As a major source of uncertainty, the spatial fluctuation of soil properties is found to have significant influence on [...]

Abstract. This work examines the Discrete Element Method (DEM), also known as the particle method, for its application in soil mechanics, specifically to calculate the tension acting on granular materials [...]

The concept of the spectral pseudo-static procedure has been developed at the Universite de Sherbrooke as an alternative to the conventional pseudo-static approach for the seismic stability analysis of clayey slopes. The destabilizing effect of an earthquake is approximated, in the new approach, by an inertial force that hyperbolically varies with depth while being proportional to the maximum acceleration of the seismic event. Its results have been rigorously verified against available static and dynamic laboratory tests, and have been extensively validated by a series of simulations performed using the computer code FLAC. Good agreements have been achieved between the results of the spectral pseudo-static procedure and complete numerical analyses, in terms of the computed safety factors and the critical slip surfaces. This implies that the spectral pseudo-static approach can be integrated into available limit equilibrium (LE) software providing a useful tool to examine the effect of dynamic soil characteristics on the proposed seismic coefficient profiles. The herein-reported study extends the previous endeavors to examine and quantify the effect of plasticity index (PI) (0%, 15%, 30%, 50%, and 100%) on the proposed formula of seismic coefficient profile using the same numerical modelling and assumptions. Original analyses were carried out considering earthquakes compatible with the seismicity of Quebec City (zone 4), and they have been repeated in the current study for earthquakes compatible with other regions having different seismicity (zones 2, 3, and 5). Based on the results of the current analyses, side-formulas were established between the spectral pseudo-static coefficient on ground surface for any value of soil plasticity index (PI) and the corresponding coefficient originally used in the main formula (PI = 30%).Key words: spectral pseudo-static, cohesive soil, plasticity index, seismic zone, failure surface.Le concept de la methode pseudo-statique spectrale a ete developpe a l'Universite de Sherbrooke comme une alternative a l'approche pseudo-statique conventionnelle pour l'analyse de la stabilite sismique des pentes argileuses. L'effet destabilisant d'un seisme est remplace, dans la nouvelle approche, par une force d'inertie qui varie hyperboliquement avec la profondeur tout en etant proportionnelle a l'acceleration maximale de l'evenement sismique. Ses resultats ont ete rigoureusement verifies a l'aide d'essais de laboratoire statiques et dynamiques disponibles, et ont ete largement valides par des series de simulations effectuees en utilisant le code informatique FLAC. De bons accords ont ete obtenus entre les resultats de la nouvelle procedure pseudo-statique spectrale et les analyses dynamiques completes, en termes de facteurs de securite et de surfaces de glissement critiques. Cela implique que l'approche pseudo-statique spectrale peut etre integree dans un logiciel base sur l'equilibre limite, fournissant un outil utile pour examiner l'effet des caracteristiques dynamiques du sol sur les profils de coefficients sismiques proposes. L'etude presentee dans cet article etend les efforts precedents pour examiner et quantifier l'effet de l'indice de plasticite (IP) (0,15, 30, 50 et 100 %) sur la formule proposee de profil de coefficient sismique en utilisant la meme modelisation numerique et hypotheses. Des analyses originales ont ete realisees en tenant compte des tremblements de terre compatibles avec la sismicite de Quebec (zone 4), repetees dans la presente etude pour les seismes compatibles avec d'autres regions de sismicite differente (zones 2, 3 et 5). Sur la base des resultats des analyses actuelles, des formules ont ete etablies entre le coefficient pseudo-statique spectral a la surface du sol pour toute valeur d'indice de plasticite (IP) du sol et le coefficient correspondant initialement utilise dans la formule principale (IP = 30 %). [Traduit par la Redaction]Mots-cles: pseudo-statique spectral, sol cohesif, indice de plasticite, zone sismique, surface de rupture., IntroductionThe pseudo-static slope stability procedures are extensively implemented in engineering practice to assess the likely seismic performance of both natural and engineered slopes. It has been proved that these procedures [...]

Dye tracing experiments provide direct visual evidence of preferential flow in the soil. In this study, we applied the Brilliant Blue tracer across three forest sites (high-mountain forest, HF; middle-mountain forest, MF; and lowmountain forest, LF) and one cultivated field (CL) in the Three Gorges Reservoir Area of China to visualise preferential flow and characterise its interaction with the surrounding soil matrix. A set of parameters was extracted from photographs of dye-stained soil profiles to measure preferential flow, including (1) the ratio of the stained area to the total area of a soil section (SAR), (2) the degree of lateral water mixing of preferential flow into the soil matrix (LWM), (3) the greatest stained depth (SD), and (4) the stained path width (SPW). The highest SAR of all of the stained areas (i.e. a measure of the degree of preferential flow) was for MF (80%), followed by LF (68%), CL (48%), and HF (30%). The higher SAR in MF and LF was likely associated with more abundant and interconnected void spaces created by roots and soil fissures. The shallower rooting depth together with the higher content of clay and soil organic matter might lead to the lowest SAR in HF, suggesting a higher likelihood of soil erosion due to surface runoff. The relatively lower SAR in CL could be a result of soil compaction after tillage destroyed soil macropores. Moreover, the spatial distribution of preferential flow with soil depth varied among slope positions. In H F and MF, macropore flow dominated the A horizon with limited lateral diffusion. However, in the subsoil, although the SAR of all of the stained areas declined, the LWM (quantified as the SAR of yellow and green patches that have a lower concentration of the dye tracer) intensified. In the sandy soils at the LF site, macropore flow via soil fissures was the major type of preferential flow that showed a limited lateral diffusion. In CL. the degree of preferential flow (mainly as finger flows) decreased with soil depth. Based on the SPW profile, flow patterns were classified along soil depth at each site. The lower degree of preferential flow and the reduced SD in agricultural soils demonstrated the substantial impact of soil management on preferential flow and thereby infiltration. Therefore, current agricultural management exacerbates surface runoff and soil erosion and causes ecological degradation and sediment deposition in the Three Gorges Reservoir Area of China. Additional keywords: Brilliant Blue, infiltration, land management, lateral water mixing, macropore, subsurface hydrology., Introduction Preferential flow in soils refers to the phenomenon of nonequilibrium flow through a small fraction of the pore space, by which water and solutes are rapidly transported to the [...]

Although many regression equations of cone penetration test tip resistance, [q.sub.c]-CPT, versus shear wave velocity, [V.sub.s], are available in the literature resulting from a substantial research effort in this topic area, the outcome of these research efforts with respect to the influence of grain size on the [V.sub.s]- [q.sub.c] correlations is in fact inconclusive because some of the suggested relationships, in common use today, either utilize irrelevant parameters or they are rather crude approximations of the [V.sub.s]-[q.sub.c] trend over a wide range of grain sizes. A closer examination of this effect would be important for better assessment of the reliability and limitations of the proposed correlations. This note discusses the plausible reasons for the inconsistency in the existing [V.sub.s]-[q.sub.c] correlations with respect to grain size through a detailed comparison of two well-known discrepant correlations referring to comparable experimental and field data. This note then goes further in its contribution to the practice of geotechnics by providing some useful recommendations to be considered in the prospective construction of [V.sub.s]-[q.sub.c] correlations, especially when particle characteristics are taken into account. Key words: stress-normalized shear wave velocity ([V.sub.s1]), stress-normalized cone tip resistance ([q.sub.c1N]), soil mean effective diameter ([D.sub.50]), soil behavior type index ([I.sub.c]), soil classification, correlation. De nombreuses relations entre la resistance en pointe du cone de penetration, [q.sub.c]-CPT, et la vitesse des ondes de cisaillement, [V.sub.s], sont disponibles dans la litterature resultant d'un effort de recherche important. Cependant, les resultats concernant l'influence de la taille des grains sur ces correlations [V.sub.s]- [q.sub.c] sont peu concluants parce que certaines d'entre elles, suggerees et couramment utilisees aujourd'hui, utilisent des parametres non pertinents ou des approximations grossieres pour une large gamme de tailles de sols. Un examen attentif de cet effet serait important pour mieux evaluer la fiabilite et les limites des correlations proposees. Dans cette note, on discute des raisons plausibles de l'incoherence entre les correlations [V.sub.s]-[q.sub.c] existantes par rapport a la taille des grains grace a une comparaison detaillee de deux correlations discordantes bien connues se referant a des donnees experimentales et de terrain comparables. Cette note va ensuite plus loin pour contribuer a la pratique de la geotechnique en fournissant quelques recommandations utiles a prendre en compte dans l'elaboration prospective des correlations [V.sub.s]-[q.sub.c] en particulier lorsque les caracteristiques des particules sont prises en compte. Mots-cles : vitesse des ondes de cisaillement normalisee ([V.sub.s1]), resistance en pointe normalisee ([q.sub.c1N]), diametre moyen des grains ([D.sub.50]), indice de comportement du sol ([I.sub.c]), classification du sol, correlation., Introduction Although field parameters (e.g., standard penetration test blow count, N-SPT, and cone penetration test tip resistance, [q.sub.c]-CPT) proffer readily available resources to estimate shear wave velocity, [V.sub.s], most of [...]

The majority of geoengineering applications occur in the unsaturated (vadose) zone, which is the near-surface region forming the connection between meteorological phenomena above and saturated ground below. The key characteristic of the unsaturated zone is that water is in tension or, put another way, pore-water pressure is negative. Moisture content, as well as most material properties, vary spatially and temporally in the unsaturated zone and coupled processes are common. In geoengineering applications in the vadose zone, unsaturated soils may be present during part or all of their design lives. The question is how or when to consider the unsaturated soils' principles in an analysis or design. Although most geoengineering applications have an unsaturated component, use of unsaturated soil mechanics in practice lingers behind the prolific number of publications due the uncertain benefit of accounting for unsaturated effects, complexity, and conservativeness among other reasons. The focus of this colloquium is to continue bridging the gap by illustrating unsaturated soils' principles using application-driven examples in the areas of capillarity as well as flow, strength, and deformation phenomena. As principles of unsaturated soils become more understood and demand increases for incorporating climate change effects in design, use of unsaturated soils' principles in practice will continue to increase. Key words: unsaturated soils, capillarity, seepage, strength, expansive soils. La majorite des applications de geoingenierie se produisent dans la zone insaturee (<< vadose >>), qui se situe dans la region proche de la surface, faisant ainsi le lien entre les phenomenes meteorologiques ci-dessus et le sol sature ci-dessous. La caracteristique cle de la zone insaturee est que l'eau est en tension ou, en d'autres termes, la pression de l'eau interstitielle est negative. La teneur en humidite, ainsi que la plupart des proprietes du materiau, varient dans l'espace et dans le temps dans la zone non saturee et les processus couples sont courants. Dans les applications de geoingenierie dans la zone vadose, les sols non satures peuvent etre presents pendant tout ou partie de ses durees de vie. La question est de savoir comment ou quand tenir compte des principes des sols non satures dans une analyse ou un plan. Bien que la plupart des applications de geoingenierie comportent une composante insaturee, l'utilisation de la mecanique des sols insatures persiste derriere le nombre important de publications en raison des avantages incertains de la prise en compte des effets insatures, de la complexite et de la prudence parmi d'autres raisons. L'objectif de ce colloque est de continuer a combler le fosse en illustrant les principes des sols non satures en utilisant des exemples axes sur l'application dans les domaines de la capillarite ainsi que des phenomenes d'ecoulement, de resistance et de deformation. Au fur et a mesure que les principes des sols insatures deviennent mieux compris et que la demande augmente pour incorporer les effets du changement climatique dans la conception, l'utilisation des principes des sols non satures dans la pratique continuera d'augmenter. [Traduit par la Redaction] Mots-cles: sols insatures, capillarite, suintement, force, sols expansifs., Introduction The majority of geoengineering applications occur in the unsaturated, or vadose zone, which can be up to hundreds of metres in depth depending on the ground profile and climate. [...]

Soil surface topography affects fundamental hydrologic processes, such as infiltration and soil water percolation. Topographic variations potentially alter both the magnitude and directions of unsaturated flow The objective of this study is to evaluate the effects of surface topography on wetting front moving patterns under different rainfall and soil conditions through combined experimental and numerical modelling studies. Specifically, laboratory-scale infiltration and unsaturated flow experiments and HYDRUS-2D modelling were conducted for different topographic surfaces, rainfall intensities, and soil types. The simulated and observed wetting front distributions were compared and evaluated. Two different stages were observed: topography-dominated two-dimensional flow and uniform one-dimensional flow. A uniformly distributed wetting front was eventually achieved although soil surfaces had dissimilar topographic characteristics. However, the timing or duration to reach such a uniform flat wetting front varied, mainly depending on surface topography, rainfall characteristics, and soil hydraulic properties. The findings from this study are important to better understand the mechanism of topography-controlled unsaturated flow, wetting front movement, and overland flow generation, and to further improve modelling of soil water flow and transport processes under such complex conditions across different scales. Additional keywords: HYDRUS, surface roughness, unsaturated flow, vadose zone., Introduction Many experimental studies have quantified wetting front movement in unsaturated soils under different conditions. For example, Bernadiner (1998) investigated the capillary microscale structure of wetting fronts, and the mechanism [...]

Introduction The paper by Pells et al. (2017) makes the case that the rock quality designation (RQD) system has essentially outlived its usefulness and is no longer effective as a [...]

Particle-size distribution (PSD) is a fundamental soil property that plays an important role in soil classification and soil hydromechanical behaviour. A continuous mathematical model representing the PSD curve facilitates the quantification of particle breakage, which often takes place when granular soils are compressed or sheared. This paper proposes a simple and continuous PSD model for granular soils involving particle breakage. The model has two parameters and is able to represent different types of continuous PSD curves. It is found that one model parameter is closely related to the coefficient of nonuniformity ([C.sub.u]) and the coefficient of curvature ([C.sub.c]), while the other represents a characteristic particle diameter. A database of 53 granular soils with 154 varying PSD curves is analyzed to evaluate the performance of the proposed PSD model, as well as that of three other PSD models in the literature. The results show that the proposed model has improved overall performance and captures the typical trends in PSD evolution during particle breakage. In addition, the proposed model is also used for assessing the internal stability of 27 widely graded soils. Key words: granular soil, particle-size distribution (PSD), mathematical model, particle breakage, internal stability. La distribution granulometrique (PSD) est une propriete de sol fondamentale qui joue un role important dans la classification des sols et le comportement hydromecanique du sol. Un modele mathematique continu representant la courbe PSD facilite la quantification de la rupture des particules, qui se deroule souvent lorsque les sols granulaires sont comprimes ou cisailles. Cet article propose un modele PSD simple et continu pour les sols granulaires impliquant une rupture des particules. Le modele a deux parametres et est capable de representer differents types de courbes PSD continu. On trouve qu'un parametre de modele est etroitement lie au coefficient de non-uniformite ([C.sub.u]) et au coefficient de courbure ([C.sub.c]) tandis que l'autre represente un diametre de particule caracteristique. Une base de donnees de 53 sols granulaires avec 154 differentes courbes PSD est analysee pour evaluer les performances du modele PSD propose, ainsi que de trois autres modeles PSD dans la litterature. Les resultats montrent que le modele propose a ameliore la performance globale et capte les tendances typiques de l'evolution du PSD lors de la rupture des particules. En outre, le modele propose est egalement utilise pour evaluer la stabilite interne de 27 sols largement classes. [Traduit par la Redaction] Mots-cles : sol granulaire, distribution granulometrique (PSD), modele mathematique, bris de particules, stabilite interne., Introduction Particle-size distribution (PSD) is a basic soil property and the main basis for soil classification. It is used in analysis of stability of granular filters (Kenney and Lau 1985; [...]

Multichannel analysis of surface waves (MASW) is a fast, low-cost, and environmentally friendly technique to estimate shear wave velocity profiles of soil sites. This paper introduces a new open- source software, MASWaves, for processing and analysing multichannel surface wave records using the MASW method. The software consists of two main parts: a dispersion analysis tool (MASWaves Dispersion) and an inversion analysis tool (MASWaves Inversion). The performance of the dispersion analysis tool is validated by comparison with results obtained by the Geopsy software package. Verification of the inversion analysis tool is carried out by comparison with results obtained by the software WinSASW and theoretical dispersion curves presented in the literature. Results of MASW field tests conducted at three sites in south Iceland are presented to demonstrate the performance and robustness of the new software. The soils at the three test sites ranged from loose sand to cemented silty sand. In addition, at one site, the results of existing spectral analysis of surface waves (SASW) measurements were compared with the results obtained by MASWaves. Key words: multichannel analysis of surface waves (MASW), dispersion analysis, inversion analysis, open-source software, shear wave velocity. L'analyse multicanal des ondes de surface (<< MASW >>) est un moyen technique rapide, peu couteux et respectueux de l'environnement pour estimer les profils de vitesse des ondes de cisaillement de sites de sols. L'article presente un nouveau logiciel a source ouverte, MASWaves, pour le traitement et l'analyse d'enregistrements des ondes de surface multicanal a l'aide de la methode MASW. Le logiciel se compose de deux parties principales; un outil d'analyse de la dispersion (la dispersion MASWaves) et un outil d'analyse d'inversion (l'inversion MASWaves). La performance de l'outil d'analyse de la dispersion est validee par la comparaison aux resultats obtenus par le logiciel Geopsy. La verification de l'outil d'analyse d'inversion est effectuee par rapport aux resultats obtenus par le logiciel WinSASW et les courbes de dispersion theoriques presentes dans la litterature. Les resultats des essais sur le terrain de MASW effectues dans trois sites dans le sud de l'Islande sont presentes afin de demontrer les performances et la robustesse de ce nouveau logiciel. Les sols a l'essai aux trois sites allant de sable lache au sable limoneux cimente. De plus, sur un site, les resultats de mesures de l'analyse spectrale des ondes de surface (<< SASW >>) ont ete compares aux resultats obtenus par MASWaves. [Traduit par la Redaction] Mots-cles : analyse multicanal des ondes de surface (MASW), analyse de la dispersion, analyse de l'inversion, logiciels a source ouverte, vitesse des ondes de cisaillement., Introduction Knowledge of the geotechnical properties of subsoil sites is essential in various civil engineering projects. The shear wave velocity of the top-most soil layers is a key parameter in [...]

Due to the formational environment and climatic variability, granite residual soils with grain-size distribution ranging from gravel to clay undergo multiple drying-wetting cycles. The influences of multiple drying-wetting cycles on the soil-water characteristic curve (SWCC) and pore-size distribution (POSD) of undisturbed granite residual soils are investigated using the pressure plate test and nuclear magnetic resonance (NMR) spin-spin relaxation time ([T.sub.2]) distribution measurement, respectively. Results show that the water-retention capacity and air-entry value decrease and pores become more uniform with increasing drying-wetting cycles. After four drying-wetting cycles, the soil reaches a nearly constant state. The POSD change of multiple drying-wetting cycle samples is consistent with the SWCC of the soils. Furthermore, a modified van Genuchten model in terms of cumulative pore volume is used to obtain the best-fit POSD of the drying-wetting cycle samples. The shape and changing tendency of both curves of SWCC and POSD are quite similar and achieved a better correlation. It can be concluded that the SWCC is strongly dependent on the POSD of the soil and NMR [T.sub.2] relaxometry can be used as an alternative to the assessment of microstructural variation of residual soils subjected to the periodic drying and wetting process. Key words: granite residual soil, drying-wetting cycles, soil-water characteristic curve (SWCC), nuclear magnetic resonance (NMR), pore-size distribution (POSD). En raison de l'environnement de formation et la variabilite climatique, les sols residuels de granit avec la distribution granulometrique allant du gravier a l'argile subissent de multiples cycles de sechage-mouillage. Les influences des cycles multiples de sechage-mouillage sur la courbe caracteristique sol-eau (SWCC) et la distribution de la taille des pores (POSD) du sol residuel non perturbe de granit sont etudiees a l'aide du test de la plaque de pression et de la mesure de la distribution temps de relaxation spin-spin ([T.sub.2]) de la resonance magnetique nucleaire (RMN), respectivement. Le resultat montre que la capacite de retention d'eau et la valeur d'entree d'air diminuent et les pores deviennent plus uniformes avec l'augmentation des cycles de sechagemouillage. Apres quatre cycles de sechage-mouillage, le sol atteint un etat presque constant. Le changement de POSD d'echantillons soumis a plusieurs cycles de sechage-mouillage cadre avec avec la SWCC des sols. En outre, un modele de van Genuchten modifie en termes de volume de pores cumulatif est utilise pour obtenir le meilleur ajustement POSD des echantillons de cycles de sechage-mouillage. La forme et la tendance changeante des deux courbes de SWCC et de POSD sont assez semblables et ont observe une meilleure correlation. On peut conclure que la SWCC est fortement dependante de la POSD du sol et que la relaxometrie RMN [T.sub.2] peut etre utilisee comme alternative a l'evaluation de la variation microstructurale des sols residuels soumis au processus de sechage et de mouillage periodiques. [Traduit par la Redaction] Mots-cles: sol residuel de granit, cycles de sechage-mouillage, courbe caracteristique sol-eau (SWCC), resonance magnetique nucleaire (RMN), distribution de la taille des pores (POSD)., Introduction Residual soils are the weathering product of their parent materials. Their engineering properties and behaviors vary widely from place to place depending upon the rock of origin and the [...]

To better understand the overall hydromechanical behaviour of interlayer soil, the compaction behaviour of one of the two components--the portion of fines ( Key words: optimum water content, maximum shear modulus, suction, compaction, soil plasticity. Afin de mieux comprendre le comportement hydromecanique global des sols, le comportement au compactage de l'une des deux composantes--la partie de fines (> definie par la valeur maximale de [G.sub.max] et la succion correspondante. La difference entre les compactages statiques et dynamiques a egalement ete expliquee en termes de valeurs de succion. [Traduit par la Redaction] Mots-cles : teneur en eau optimale, module de cisaillement maximal, succion, compaction, plasticite du sol., Introduction In most of the French conventional railway track-beds, after several years of traffic loading, a new layer namely interlayer was formed mainly by the interpenetration of ballast and fine [...]

Limit state design, incorporated into many recent geotechnical design codes, introduces the application of partial or resistance factors to selected characteristic values. Partial or resistance factors are usually set by national standard organizations, while characteristic values of geotechnical parameters are selected by engineers, often based on sparse measurement data combined with subjective engineering experience and judgment. Due to this subjective selection and individual judgment, the characteristic value derived by different engineers from the same dataset may vary greatly, especially when the test data contain significant variability. To address this issue, a new method based on Bayesian compressive sampling (BCS) is proposed in this study. BCS is able to reconstruct a high-resolution geotechnical property profile from sparse measurement data and quantify the uncertainty, e.g., confidence interval (CI) associated with the interpreted profile. The quantified uncertainty in the BCS has a clear statistical meaning: the corresponding confidence level for a CI from the BCS is the expected coverage proportion (i.e., fraction) of the complete profile that falls within the CI, if all data points along depth can be measured to provide the complete profile. This statistical meaning can be used to facilitate objective determination of characteristic values for geotechnical properties. Key words: reliability-based design, Bayesian compressive sampling, compressive sensing, sparse measurement data, site investigation. La conception etats limites, integres dans de nombreux codes de conception geotechnique, presente l'application de facteurs de resistance de resistance ou partielle a certaines valeurs de caracteristique. Des facteurs de resistance ou partiels sont habituellement fixes par les organismes de normalisation, tandis que les valeurs caracteristiques des parametres geotechniques sont selectionnees par les ingenieurs, souvent basees sur des donnees de mesure combinee a l'experience en genie et de jugement subjectif. En raison de cette selection subjective et ce jugement individuel, la valeur caracteristique derivee par differents ingenieurs du meme jeu de donnees peut varier considerablement, en particulier lorsque les donnees d'essai contiennent une variabilite importante. Pour resoudre ce probleme, une nouvelle methode basee sur l'echantillonnage en compression bayesien (<< BCS >>) est proposee dans cette etude. BCS est capable de reconstruire une propriete geotechnique a haute resolution a partir de donnees de mesure profil clairseme et de quantifier l'incertitude, par exemple, l'intervalle de confiance (IC) associe a l'interpretation de profil. L'incertitude quantifiee dans le BCS a une signification statistique claire: le niveau de confiance correspondant pour un IC de la BCS est la couverture prevue (proportion) de la fraction profil complet qui releve de l'IC, si tous les points de donnees le long de la profondeur peuvent etre mesures pour fournir le profil complet. Cette signification statistique peut etre utilisee pour faciliter l'objectif de determination des valeurs caracteristiques des proprietes geotechniques. [Traduit par la Redaction] Mots-cles : conception basee sur la fiabilite, echantillonnage compression bayesienne, detection de compression, donnees clairsemees de mesure, etude de site., Introduction Limit state design methods have been recently incorporated into many geotechnical codes of practice throughout the world, e.g., Eurocode 7 (CEN 2004), the AASHTO (1998) bridge code, and the [...]

Hydraulic anisotropy behavior of unsaturated soil has not been fully investigated. Direct laboratory measurement and indirect determination of hydraulic anisotropy under a drying condition were carried out on statically compacted specimens having different initial conditions. Direct measurement of permeability was carried out using an unsaturated triaxial permeameter whereas indirect determination of permeability was performed through statistical estimation via a measured drying soil-water characteristic curve (SWCC). In this research, two orientations--specifically horizontal-layering (HL) and vertical-layering (VL) orientations--were prepared for a given specimen from statically compacted homogeneous sand-kaolin. The results from both direct measurement and indirect determination of hydraulic anisotropy were in good agreement. Hydraulic anisotropy under an unsaturated condition was found to be similar with that in a saturated condition. Moreover, hydraulic anisotropy was reflected in the ratio of transient time during the direct measurements of HL and VL specimens at high matric suctions. In contrast, in the indirect method, hydraulic anisotropy was reflected in the ratio of equalization time during SWCC tests at matric suctions higher than the air-entry value of the soil. Key words: unsaturated soil, hydraulic anisotropy, permeability, soil-water characteristic curve, laboratory experiment. Le comportement d'anisotropie hydraulique de sol non sature n'a pas ete pleinement examine. La mesure directe de laboratoire et la determination indirecte de l'anisotropie hydraulique sous condition de sechage ont ete effectuees sur des specimens compactes statiquement ayant differentes conditions initiales. La mesure directe de la permeabilite a ete realisee a l'aide du permeametre triaxial non sature alors que la determination indirecte de permeabilite a ete effectuee par l'intermediaire de l'estimation statistique via la mesure de la courbe de caracteristique sol-eau de sechage (SWCC). Dans cette recherche, deux orientations--plus precisement la disposition horizontale (HL) et verticale (VL)--ont ete preparees pour un specimen donne de sable-kaolin homogene compacte. Les resultats a la fois de mesures directes et de la determination indirecte de l'anisotropie hydraulique etaient en bon accord. L'anisotropie hydraulique sous condition insaturee etait similaire a celle de l'etat sature. En outre, l'anisotropie hydraulique a ete refletee dans le rapport de temps transitoire pendant la mesure directe des specimens HL et VL a des hautes succions matrices. D'autre part dans la methode indirecte, l'anisotropie hydraulique a ete refletee dans le rapport de temps de perequation au cours des essais a des succions matrices SWCC superieures a la valeur d'entree d'air du sol. [Traduit par la Redaction] Mots-cles: sol non sature, anisotropie hydraulique, permeabilite, courbe caracteristique sol-eau, experience en laboratoire., Introduction Hydraulic characteristics of soil are described mainly by its permeability and its soil-water characteristic curve (SWCC). Coefficient of permeability relates flow rate to driving potential, which is primarily due [...]

A series of incremental loading oedometer tests was conducted on pure clays and sand-clay mixtures with various sand/clay ratios and clay mineral compositions. The void indexes [I.sub.v] and [I.sub.vH] were introduced to evaluate their intrinsic compressibility. Test results revealed that [I.sub.v] was more suitable for depicting the compression behavior of pure clays than [I.sub.vH]; whereas, for the compressibility of sand-clay mixtures, the normalized compression line by using [I.sub.v] was obviously different from that of pure clays and traditional soils due to the presence of sand particles. Therefore, a four-phase analysis framework of sand -clay mixtures was introduced to unify the intrinsic compression behavior of soils with and without sands. It was found that the updated clay void index [I.sub.vc] parameter was effective to unify the soil's compression behavior by excluding the influence of sand particles in clays before the sand skeleton formation. After the formation of the sand skeleton, the cluster particles change the stress distribution of mixtures, leading to less stress being applied on the clay matrix and thus the bifurcation of the intrinsic compression behavior. Key words: sand-clay mixture, intrinsic compression behavior, four-phase analysis framework, updated clay void index, sand skeleton. Une serie d'essais redometriques de chargement par increment a ete effectuee sur des argiles pures et sur des melanges sable-argile avec diverses/argile et mineral d'argile. Les indices de vides [I.sub.v] et [I.sub.vH] ont ete introduits afin d'evaluer leur compressibilite intrinseque. Les resultats d'essais ont revele que [I.sub.v] etait plus approprie pour decrire le comportement en compression d'argiles pures que [I.sub.vH], considerant que, pour la compressibilite du melange sable-argile, la ligne de compression normalisee avec l'utilisation de [I.sub.v] etait evidemment differente de celle des argiles pures et des sols traditionnels en raison de la presence de particules de sable. Par consequent, un cadre d'analyse en quatre phases du melange sable-argile a ete introduit afin d'unifier le comportement en compression intrinseque des sols avec et sans l'utilisation des sables bitumineux. Il a ete constate que le parametre [I.sub.vc] de l'index de vides d'argile mise a jour a ete efficace pour unifier le comportement en compression des sols par l'exclusion de l'influence des particules de sable dans les argiles avant la formation du squelette. Apres la formation du squelette du sable, les particules du groupement changent la distribution de contrainte des melanges, ce qui conduit a moins de contrainte appliquee sur la matrice argileuse et donc la bifurcation du comportement de la compression intrinseque. [Traduit par la Redaction] Mots-cles: melange sable-argile, comportement de la compression intrinseque, cadre d'analyse en quatre phases, indice de vide d'argile mis a jour, squelette de sable., Introduction Many studies have been carried out to evaluate the compression behavior of natural sedimentary soils (Houston and Mitchell 1969; Hight et al. 1987; Burland 1990; Cotecchia and Chandler 2000). [...]

A combined constitutive model is developed for the creep behavior of frozen soil in an unconfined condition. The model is obtained by coupling two stress- and time-dependent models, which are responsible for the primary and tertiary creep stages. The model parameters are dependent on temperature and can be readily determined from the strain rate-time curves at two creep stresses. The model performance is demonstrated by simulating the complete strain-time and strain rate-time curves (including primary, secondary, and tertiary stages) of frozen sand and frozen clay in uniaxial creep tests under different creep stresses. Moreover, two equations are obtained from the combined model. One shows a good capability in describing the relationship between creep strength and the time to creep failure. The other makes an excellent prediction of the steady flow rate in a typical creep process. Both equations can reflect the effects of stress and temperature on the creep behavior of frozen soil. Key words: frozen soil, creep, steady flow rate, creep strength, constitutive model. Un modele constitutif combine est elabore pour le comportement en fluage de sol gele dans des conditions non confinees. Le modele est obtenu par le couplage de deux modeles dependants en contrainte temps, qui sont responsables des etapes de fluages primaires et tertiaires. Les parametres du modele sont dependants de la temperature et peuvent etre facilement determines a partir des courbes de taux de temps a deux contraintes de fluage. La performance du modele est demontree par la simulation de l'ensemble des courbes de la deformation-temps et du taux de deformation-temps (y compris les etapes primaires, secondaires et tertiaires) de sable gele et d'argile gelee en essais de fluage uniaxial sous differentes contraintes de fluage. En outre, deux equations sont obtenues a partir du modele combine. L'une montre une bonne capacite dans la description de la relation entre la resistance au fluage et le temps a la defaillance de fluage. L'autre fait une excellente prediction des taux d'ecoulement reguliers dans un processus de fluage. Les deux equations peuvent refleter les effets de contrainte et de la temperature sur le comportement de fluage du sol gele. [Traduit par la Redaction] Mots-cles: sol gele, fluage, debit d'ecoulement constant, resistance au fluage, modele constitutif., Introduction For engineering construction projects in permafrost regions, the creep and time-dependent strength of frozen ground are important to ensure the long-term stability of the structures concerned. Since the pioneering [...]

Although evapotranspiration-induced matric suction for single species has been widely studied, little is known about how mixed-species planting would affect plant growth and induced matric suction. This study aims to explore the effects of grass-tree interaction on their growth and induced matric suction during evapotranspiration (ET) and rainfalls. Field monitoring was carried out to measure matric suction responses in compacted soil that was vegetated with (i) single tree species, Schefflera heptaphylla, and (ii) mixed species of the trees and a grass species, Cynodon dactylon. In each condition, three tree spacings (120,180, and 240 mm) were planted. When tree spacing increased from 120 to 240 mm, the peak tree root area index (RAI, for fine roots with diameter Key words: mixed-species planting, plant spacing, plant growth, evapotranspiration, matric suction. Bien que la succion matricielle induite par l'evapotranspiration pour une seule espece ait ete largement etudiee, on sait peu de choses sur la facon dont la plantation d'especes mixtes aurait une incidence sur la croissance des plantes et sur la succion matricielle induite. Cette etude vise a etudier les effets de l'interaction herbe-arbre sur leur croissance et sur leur succion matricielle induite par l'evapotranspiration (ET) et par les precipitations. La surveillance sur le terrain a ete effectuee pour mesurer les reponses de succion matricielle dans le sol compacte qui etait en forme vegetale avec : (i) des especes d'arbres uniques, Schefflera heptaphylla et (ii) des especes d'arbres mixtes et une espece d'herbe, Cynodon dactylon. Dans chaque condition, trois espacements d'arbres (120, 180 et 240 mm) ont ete plantes. Lorsque l'espacement entre les arbres a augmente de 120 a 240 mm, l'indice pic de la racine de l'arbre (RAI, pour les racines fines de diametre inferieur a 2 mm) a diminue de 16 %, mais la RAI des herbes pics a augmente de 29 %. Dans les parcelles de plantation mixte, la succion matricielle induite par l'ET pour l'espacement d'arbres de 240 mm a ete 20 % superieure a celle de l'espacement de 180 mm en raison de la contribution accrue de l'absorption d'eau des racines d'herbes, car les arbres etaient plus espaces. Sans l'herbe, on a observe une tendance inverse, car l'interaction entre les arbres et les arbres a ete reduite a des intervalles larges. La succion matricielle pic induit par l'ET a une correlation lineaire significative avec le RAI. Pendant les pluies, la plus grande succion matricielle a ete preservee pour le cas d'un espacement de 240 mm en raison de la plus grande reduction de la conductivite hydraulique du sol par la presence de racines. [Traduit par la Redaction] Mots-cles : plantation d'especes mixtes, espacement des plantes, croissance des plantes, evapotranspiration, succion matricielle., Introduction Soil bioengineering using vegetation has been recognized as an ecologically and environmentally friendly technique that can affect the stability of geotechnical infrastructure such as man-made or engineered slopes. To [...]

The stability of cut slopes is greatly influenced by seasonal pore-water pressure variations under the combined effect of rainfall and vegetation. However, predicting soil-atmosphere interaction is not straightforward, due to the complexity of both the boundary conditions involved and the hydromechanical behaviour of soils, which is coupled and highly nonlinear, rendering the use of numerical tools, such as finite element analysis, necessary. This paper discusses the numerical modelling of soil-atmosphere interaction and presents the analysis of a slope cut in London clay in a highly vegetated area. The whole life cycle of the slope is considered with phases of low and high water demand vegetation and vegetation clearance. The analysis results indicate that dense vegetation is associated with high factors of safety, but may induce large differential displacements, which are likely to affect the serviceability of the slope. Vegetation clearance, however, may initiate instability, highlighting the need for effective vegetation management to achieve a balance between serviceability and ultimate limit states. Although the case considered is representative of southeast England, it introduces the necessary tools for realistic numerical analysis of soil-atmosphere interaction. Key words: slope stability, serviceability, vegetation, precipitation, soil-atmosphere interaction. La stabilite des pentes entaillees est fortement influencee par les variations de pression de l'eau interstitielle saison nieres sous l'effet combine des precipitations et de la vegetation. Cependant, predire l'interaction sol-atmosphere n'est pas si simple, en raison de la complexite des deux conditions aux limites en cause et le comportement hydromecanique des sols, qui est couple et fortement non lineaire, ce qui rend l'utilisation d'outils numeriques, tels que l'analyse des elements finis neces saire. Cet article traite la modelisation numerique de l'interaction sol-atmosphere et presente l'analyse d'une pente entaillee dans l'argile de Londres dans une zone tres vegetalisee. L'ensemble du cycle de vie de la pente est considere avec des phases de demande en eau basse et haute de la vegetation et la clairance de la vegetation. Les resultats de l'analyse indiquent que la vegetation dense est associee a des facteurs eleves de securite, mais peut induire des deplacements differentiels qui sont susceptibles d'affecter l'etat de fonctionnement de la pente. L'enlevement de la vegetation, cependant, peut declencher l'instabilite, soulignant la necessite d'une gestion efficace de la vegetation afin de parvenir a un equilibre entre la fonctionnalite et les etats limites ultimes. Bien que le cas considere est representatif du Sud est de l'Angleterre, il presente les outils necessaires a l'analyse numerique realiste de l'interaction sol-atmosphere. [Traduit par la Redaction] Mots-cles: stabilite des pentes, facilite d'entretien, vegetation, precipitations, interaction sol-atmosphere., Introduction It has long been established that one of the main factors affecting the performance of infrastructure slopes (cut and embankment slopes) is the magnitude and variation of pore-water pressures [...]

Soil bioengineering using vegetation has been recognised as an environmentally friendly solution for shallow slope stabilization. Plant transpiration induces suction in the soil, but its effects on slope stability are often ignored. This study investigates the influences of transpiration-induced suction and mechanical reinforcement of different root geometries (i.e., tapand heart-shaped) to the slope stability subjected to an intense rainfall with an intensity of 70 mm/h (prototype scale; corresponding to a return period of 1000 years), via centrifuge modelling. New model roots that have scaled mechanical properties close to real roots were used to simulate transpiration-induced suction in the centrifuge. Transient seepage analyses were performed using SEEP/W to back-analyse the suction responses due to transpiration and rainfall. Subsequently, the backanalysed suction was used to assess the factor of safety of the slopes using SLOPE/W. It is revealed that heart-shaped roots provided greater stabilization effects to a 60[degrees] clayey sand slope than tap-shaped roots. The heart-shaped roots induced higher suction, leading to 14% reduction of rainfall infiltration and 6% increase in shear strength. Although transpiration-induced suction in a 45[degrees] slope was reduced to zero after the rainfall, mechanical root reinforcement was found to be sufficient to maintain slope stability. Key words: slope stability, transpiration, matric suction, root geometry, unsaturated soils, centrifuge modelling. La bio-ingenierie du sol en utilisant la vegetation a ete reconnue comme une solution respectueuse de l'environnement pour la stabilisation d'une pente peu profonde. La transpiration vegetale induit la succion dans le sol, mais ses effets sur la stabilite des pentes sont souvent ignores. Cette etude examine les influences de la succion induite par la transpiration et un renforcement mecanique des differentes geometries de racines (c.-a-d. et en forme de taraud et de creur) a la stabilite des pentes soumises a une pluviometrie intense avec une intensite de 70 mm/h (echelle de prototype, ce qui correspond a une periode de retour de 1000 ans), via la modelisation centrifugeuse. Les nouvelles racines modeles qui ont une echelle des proprietes mecaniques proche de racines reelles ont ete utilisees pour simuler la succion induite par la transpiration dans la centrifuge. Les analyses d'infiltration transitoires ont ete effectuees en utilisant SEEP/W pour analyser a nouveau les reponses de succion en raison de la transpiration et des precipitations. Par la suite, la succion analysee a nouveau a ete utilisee pour evaluer le facteur de securite des pentes en utilisant SLOPE/W. Il est revele que les racines en forme de creur ont offert des effets plus importants de stabilisation a une pente de 60 [degrees] de sable argileux que des racines en forme de taraud. Les racines en forme de creur ont induit une succion plus elevee, ce qui a engendre une reduction d'infiltration des precipitations de 14 % et une augmentation de la resistance au cisaillement de 6 %. Bien que la succion induite par la transpiration dans une pente de 45 [degrees] ait ete ramenee a zero apres la pluie, un renforcement mecanique par les racines a ete juge suffisant pour maintenir la stabilite de la pente. [Traduit par la Redaction] Mots-cles: stabilite des pentes, transpiration, succion matricielle, geometrie de la racine, sols non satures, modelisation par centrifugeuse., Introduction Vegetation has been generally recognised as an environmentally friendly alternative that could be used for ecological restoration (Hau and Corlett 2003) and also enhance slope stability against rainfall (Barker [...]

Resilient modulus has been used for decades as an important parameter in pavement structure design. Resilient modulus, like other elasticity moduli, increases with increasing confining stress and decreases with increasing deviatoric stress. Several constitutive models have been proposed in the literature to calculate resilient modulus as a function of stress state. The most recent model, recommended by the Mechanistic-empirical pavement design guide (MEPDG) and used in this paper, calculates resilient modulus as a function of bulk stress, octahedral shear stress, and three fitting coefficients: [k.sub.1], [k.sub.2], and [k.sub.3]. Work in this paper presents a novel approach for predicting resilient modulus of subgrade soils at various stress levels based on light-weight deflectometer (LWD) data. The proposed model predicts the MEPDG resilient modulus model coefficients ([k.sub.1], [k.sub.2], and [k.sub.3]) directly from the ratio of applied stress to surface deflection measured during LWD testing. The proposed model eliminates uncertainties associated with needed input parameters for surface modulus (ELWD) calculation, such as the selection of an appropriate value of Poisson's ratio for the soil layer and shape factor. The proposed model was validated with independent data from other studies reported in the literature. Key words: resilient modulus, light-weight deflectometer, subgrade, Mechanistic-empirical pavement design guide (MEPDG). Un module resilient a ete utilise pendant des decennies comme un parametre important dans la conception de la structure de la chaussee. Un module elastique, comme d'autres modules d'elasticite, augmente avec l'augmentation de contrainte de confinement et adoucit avec l'augmentation de contrainte deviatorique. Plusieurs modeles de comportement ont ete proposes dans la litterature pour calculer le module de resilience en fonction de l'etat de contrainte. Le modele le plus recent, recommande par <> (MEPDG) et utilise dans le present document, calcule le module elastique en fonction de la contrainte en vrac, contrainte de cisaillement octaedre et trois coefficients d'ajustement, [k.sub.1], [k.sub.2], et [k.sub.3]. Les travaux dans ce document presente une nouvelle approche pour predire le module elastique des sols de fondation a differents niveaux de contrainte basee sur des donnees avec un deflectometre a poids leger (LWD). Le modele propose prevoit les coefficients de modele de module elastique MEPDG ([k.sub.1], [k.sub.2], and [k.sub.3]), directement a partir du rapport de la contrainte appliquee a la deviation de surface mesuree au cours des essais LWD. Le modele propose elimine les incertitudes associees aux parametres d'entree necessaires pour le calcul du module de surface (ELWD) comme la selection d'une valeur appropriee du rapport de Poisson de la couche de sol et le facteur de forme. Le modele propose a ete valide avec des donnees independantes provenant d'autres etudes rapportees dans la litterature. [Traduit par la Redaction] Mots-cles: module de resilience, deflectometre a poids leger, fondation, <>(MEPDG)., Introduction The use of resilient modulus ([M.sub.r]) has been substituted for the California bearing ratio (CBR) in pavement design to consider the deformation behavior of base and subgrade layers under [...]

This paper aims to provide a comprehensive picture of the sand responses during secondary compression and rebound based on experimental characterizations. The experiment was carried out on dry Leighton Buzzard sand using a modified direct shear box equipped with tactile pressure sensors for the stress measurements and bender elements for stiffness (i.e., [G.sub.hv] and [G.sub.hh]) monitoring. It was found that secondary compression and rebound followed the same deformation trends as primary compression and rebound to continuously contract and expand, respectively. The deformation characteristics determined the changes in the associated soil properties; therefore, the opposite soil behavior during secondary compression and rebound was observed. During secondary compression, the corresponding void change, deviatoric strains [ζ.sub.q], and the deviatoric strain rate [[??].sub.q] increased with increasing vertical stress [σ'.sub.v] or deviatoric stress q because the sample crept more easily under a higher [σ'.sub.v] or q. The compression deformation gave rise to an increase in the horizontal stress [σ'.sub.h] and associated coefficient of earth pressure at rest [K.sub.o]. The soil stiffness also increased as the contact normal forces became more homogenized. During secondary rebound, the sample expanded unabated no matter whether [σ'.sub.v] was greater or smaller than [σ'.sub.h]. The corresponding void ratio change, [ζ.sub.q], and [??].sub.q] increased with decreasing [σ'.sub.v] or q because the sample expanded more easily under a lower [σ'.sub.v] or q. The expansion gradually reduced ah along with the associated [K.sub.o] value. The sample stiffness continued to decrease, and contact force homogenization was not observed. Key words: secondary compression, secondary rebound, coefficient of earth pressure at rest ([K.sub.o]), tactile pressure sensor, stress path. Le present article vise a fournir, a partir de caracterisations experimentales, un apercu complet du comportement d'un echantillon de sable au cours de mecanismes de compression et de soulevement secondaires. Une experience a ete realisee sur du sable sec de Leighton Buzzard au moyen d'une boite de cisaillement direct modifiee et equipee de capteurs de pression tactiles permettant de mesurer les contraintes et d'elements piezoceramiques pour surveiller en continu la rigidite (c.-a.-d. [G.sub.hv] et [G.sub.hh]). On constate que la compression et le soulevement secondaires produisent le meme type de deformation que la compression et le soulevement primaires, de maniere a respectivement se contracter et se dilater de facon continue. Les caracteristiques des deformations observees influent sur les variations des proprietes du sol qui en decoulent. Par consequent, on observe un comportement inverse du sol durant les mecanismes de compression et de soulevement secondaire. Au cours de la compression secondaire, la variation de l'indice des vides, les deformations deviatoriques [ζ.sub.q] et le taux de deformation deviatorique [[??].sub.q] observes augmentent avec la contrainte verticale [σ'.sub.v] ou avec la contrainte deviatorique q, du fait que l'echantillon se deforme plus facilement sous l'effet d'une valeur elevee de [σ'.sub.v] ou q. La deformation en compression a pour effet d'augmenter la contrainte horizontale [σ'.sub.h] et la valeur du coefficient de pression des terres au repos [K.sub.o] correspondante. La rigidite du sol augmente egalement a mesure que les forces normales de contact s'homogeneisent. Durant le mecanisme de soulevement secondaire, l'echantillon se dilate continuellement, que soit superieure ou inferieure a [σ'.sub.h]. La variation d'indice des vides et les valeurs de [ζ.sub.q], et de [[??].sub.q] alors observes augmentent lorsque [σ'.sub.v] ou q diminuent, car l'echantillon se dilate plus facilement sous l'effet d'une faible valeur de [σ'.sub.v] ou de q. La dilatation a pour effet de faire progressivement diminuer la valeur de [σ'.sub.h] ainsi que la valeur de [K.sub.o] correspondante. La rigidite de l'echantillon continue a diminuer et l'on n'observe aucune homogeneisation des forces de contact. [Traduit par la Redaction] Mots-cles : compression secondaire, soulevement secondaire, orientees le long de l'axe ([K.sub.o]), capteur de pression tactile, chemin de contrainte., Introduction The coefficient of earth pressure at rest, [K.sub.o], is an important stress state parameter in engineering design. All soils age, and their engineering properties vary with time (Schmertmann 1991). [...]

This paper presents a comprehensive experimental investigation on shrinkage and soil-water retention behaviour at macroscale and microscale of four natural Australian soils upon drying and wetting. Both reconstituted and intact states were tested. First, a comprehensive physicochemical characterization of the four soils was performed to provide a complete picture of the mineralogical composition and surface properties as well as different initial structure associated with reconstituted and intact states. Then, macroscale testing was conducted and complemented by microstructural analyses through mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) observations. These provided a comprehensive picture of the microfabric evolution of the soils tested along the drying- wetting path. All the experimental results were discussed in a coupled multi- scale manner. Key words: expansive soils, shrinkage, water retention, microstructure, mercury intrusion porosimetry (MIP). Le present article decrit une etude experimentale et exhaustive portant sur les mecanismes de retention d'eau et de contraction observes aux echelles macroscopique et microscopique dans des sols naturels australiens soumis a un assechement et une humidification. L'etat reconstitue et l'etat intact ont tous deux ete mis a l'essai. Dans un premier temps, on a procede a une caracterisation physicochimique des quatre sols etudies afin de fournir un portrait complet de la composition mineralogique et des proprietes de surface de ces sols ainsi que des differentes structures initiales associees a l'etat reconstitue et a l'etat intact. Ensuite, on a effectue des essais a l'echelle macroscopique et des analyses microstructurales par porosimetrie au mercure (PM) et par microscopie electronique a balayage (MEB). Ces essais et analyses ont fourni un apercu complet des transformations microstructurales des sols tout au long du processus d'assechement-humidification des sols. Tous les resultats experimentaux obtenus ont ete analyses a l'aide d'une methode couplee multiechelle. [Traduit par la Redaction] Mots-cles : sols gonflants, contraction, retention d'eau, microstructure, porosimetrie au mercure (PM)., Introduction Reactive soils, also called expansive soils, are notoriously problematic for infrastructure because they experience significant volume changes upon drying and wetting. The issue is particularly relevant for routine foundation [...]

This paper focuses on the calculation of probability of failure of simple unreinforced slopes and the influence of the magnitude of cross correlation between soil parameters on numerical outcomes. A general closed-form solution for cohesive slopes with cross correlation between cohesion and unit weight was investigated and results compared with cases without cross correlation. Negative cross correlations between cohesion and friction angle and positive cross correlations between cohesion and unit weight, and friction angle and unit weight were considered in the current study. The factors of safety and probabilities of failure for the slopes with uncorrelated soil properties were obtained using probabilistic slope stability design charts previously reported by the writers. Results for cohesive soil slopes and positive cross correlation between cohesion and unit weight are shown to decrease probability of failure. Probability of failure also decreased for increasing negative cross correlation between cohesion and friction angle, and increasing positive correlation between cohesion and unit weight, and friction angle and unit weight. Probabilistic slope stability design charts presented by the writers in an earlier publication are extended to include cohesive-frictional (c-φ) soil slopes with and without cross correlation between soil input parameters. An important outcome of the work presented here is that cross correlation between random values of soil properties can reduce the probability of failure for simple slope cases. Hence, previous probabilistic design charts by the writers for simple soil slopes with uncorrelated soil properties are conservative (safe) for design. This study also provides one explanation why slope stability analyses using uncorrelated soil properties can predict unreasonably high probabilities of failure when conventional estimates of factor of safety suggest a stable slope. Key words: slope stability, probabilistic analysis, cross correlation, Monte Carlo simulation. Le present article decrit le calcul de probabilite de rupture de pentes simples non consolidees et l'influence de l'amplitude des correlations croisees entre les parametres du sol sur les resultats numeriques obtenus. On a etudie une solution generale de type ferme s'appliquant aux pentes cohesives pour laquelle il existe une correlation croisee entre la cohesion et le poids unitaire et les resultats obtenus ont ete compares a des cas pour lesquels il n'existe pas une telle correlation. Dans la presente etude, on a tenu compte des correlations croisees negatives entre la cohesion et l'angle de frottement ainsi que des correlations croisees positives entre la cohesion et le poids unitaire. Les facteurs de securite et les probabilites de rupture des pentes dont les proprietes du sol ne sont pas correlees ont ete obtenus a l'aide d'abaques probabilistes de stabilite des pentes precedemment fournis par les auteurs. Les resultats obtenus dans le cas des pentes de sols cohesifs et la correlation croisee positive entre la cohesion et le poids unitaire semblent avoir pour effet de diminuer la probabilite de rupture. En outre, la probabilite de rupture diminue lorsque la correlation croisee negative entre la cohesion et l'angle de frottement augmente, lorsque la correlation positive entre la cohesion et le poids unitaire et la correlation entre l'angle de frottement et le poids unitaire augmentent. Le champ d'application des abaques probabilistes de stabilite des pentes presentes par les auteurs dans une publication precedente est etendu pour inclure les pentes des sols de type cohesive-frictionnelle (c-φ) pour lesquels il existe ou non une correlation croisee entre les parametres de depart caracterisant le sol considere. Une des conclusions importantes de la presente etude est que la correlation croisee entre les valeurs aleatoires des parametres du sol peut avoir pour effet de reduire la probabilite de rupture dans le cas de pentes simples. Ainsi, les abaques probabilistes fournis precedemment par les auteurs dans le cas de pentes simples de sols dont les proprietes ne sont pas correlees restent assez prudents (fiables) pour pouvoir etre utilises en conception. La presente etude explique egalement comment les analyses de stabilite des pentes effectuees a l'aide de parametres de sol non correles peuvent produire des predictions de probabilites de rupture anormalement elevees alors que les estimations habituelles du facteur de securite montrent que la pente consideree est stable. [Traduit par la Redaction] Mots-cles: stabilite des pentes, analyse probabiliste, correlation croisee, simulation de Monte-Carlo., Introduction Slope stability charts are used routinely to estimate the conventional factor of safety of unreinforced slopes with isotropic, homogeneous soil properties, and simple geometry. Design charts by Taylor (1937), [...]

Depending on the state paths, loading-wetting of compacted unsaturated soils can exhibit complex volumetric behaviour, such as swelling, collapse, collapse followed by swelling, swelling followed by collapse, and swelling pressure development. Microscopically, these behaviours arise from complex interactions among applied stresses, air- water pressure deficit or suction at the water menisci, moisture content or degree of saturation in the voids, and the nature of the micro- and macrosoil aggregates of compacted soils that depend on the level of suction. While significant advances have been made in modelling hydromechanical behaviour of compacted unsaturated soils taking these interactions into account, input parameter determination requires advanced testing equipment and the testing processes can be very time-consuming. In 2012, a relatively simple and practical framework within the void ratio--moisture ratio (water volume / solid volume)--net stress space (referred to as the MPK framework) has been proposed by Kodikara to explain- predict these state paths. A desirable feature of this framework is that it identifies a direct link between the well- known compaction curve and the compacted soil constitutive behaviour. This paper presents a comprehensive series of tests on statically compacted soils, the results of which are in close agreement with this framework. Two soil types, namely lightly reactive kaolin and more reactive clay (referred to as Merri Creek soil), were used in the testing. The soils were prepared with different moisture contents from the dry state and statically compacted at constant water content to obtain void ratio--moisture ratio--net stress constitutive surfaces, as well as soil specimens for state path tests. The state path test results of yielding under loading, collapse under wetting, swelling pressure development, and change in yield pressure due to wetting are explained within this framework. In addition, some published data on a silty soil mixture were also analysed, highlighting that the framework is valid, regardless of the degree of reactivity of the soil. Suction was not measured in the authors' experiments, as it was not required to explain the above state paths according to this framework. However, it is recognised that suction is the conjugate state variable to the moisture content. Therefore, in future experiments, suction will be measured and its role will be fully explained within the framework, adding more generality. Key words: compacted soils, void ratio--moisture ratio--net stress space (MPK) framework, unsaturated soils, collapse, swelling pressure. En fonction des chemins d'etat, le chargement et l'humidification de sols compactes non satures peuvent entrainer des comportements volumetriques complexes, tels qu'un gonflement, un effondrement, un effondrement suivi d'un gonflement, un gonflement suivi d'un effondrement ou une augmentation de la pression de gonflement. A l'echelle microscopique, ces comportements apparaissent sous l'effet d'interactions complexes entre les contraintes exercees, d'une pression negative a l'interface air-eau ou d'un phenomene de succion sous forme d'un menisque concave a la surface de l'eau, de la teneur en eau ou du degre de saturation dans les vides et de la nature des microgranulats et des macrogranulats de sols compactes, laquelle depend de l'intensite de la succion. Bien que des progres importants aient ete accomplis dans la modelisation du comportement hydromecanique de sols compactes non satures, laquelle tient compte de ces interactions, la determination des parametres de depart necessite l'utilisation d'appareils d'essais sophistiques et la realisation d'essais peut prendre beaucoup de temps. Recemment, une methode pratique et relativement simple, utilisant l'indice des vides, le coefficient d'humidite (volume d'eau/volume solide) et les contraintes nettes (appelee methode MPK), a ete proposee par Kodikara en 2012 pour expliquer et predire ces chemins d'etat. On desire que cette methode soit capable de mettre en evidence un lien direct entre la courbe de compactage deja connue et le comportement constitutif du sol compacte. Le present article presente une serie complete d'essais realises sur des sols soumis a un compactage statique, les resultats de ces essais semblant bien concorder avec la methode MPK. Deux types de sols, soit un sol compose de kaolin legerement reactif et un sol d'argile, plus reactive ou << sol de Merri Creek >>, ont ete utilises dans le cadre des essais. Des echantillons de sol ayant differentes teneurs en eau ont ete prepares a partir de l'etat sec et soumis a un compactage statique a teneur en eau constante, de maniere a ce que l'on obtienne des surfaces constitutives comportant l'indice de vide, le coefficient d'humidite et les contraintes nettes, ainsi que des specimens de sol destines aux essais de caracterisation des chemins d'etat. Les resultats de ces derniers essais, relatifs a la rupture sous l'effet d'une charge, a l'effondrement sous l'effet de l'humidification, a l'augmentation de la pression de gonflement et aux variations de pression rupture dues a l'humidification, sont expliques a l'aide de la methode MPK. En outre, certaines donnees publiees et relatives a un echantillon de sol limoneux sont analysees et permettent d'affirmer que cette methode est valide, quel que soit le niveau de reactivite du sol considere. La succion n'a pas ete mesuree dans le cadre des experiences realisees par les auteurs, cela n'etant pas necessaire pour expliquer les chemins d'etats mentionnes cidessus en fonction de la methode MPK. Cependant, on a admis que la succion etait une variable d'etat associee a la teneur en eau. Par consequent, lors de futures experiences, la succion sera mesuree et son role sera integralement explique a l'aide de la methode MPK, ce qui permettra de faire davantage de generalisations. [Traduit par la Redaction] Mots-cles : sols compactes, methode pratique utilisant l'indice des vides, le coefficient d'humidite et les contraintes nettes (MPK), sols non satures, effondrement, pression de gonflement., Introduction For the last half century, modelling of the hydromechanical behaviour of unsaturated soils has been a frontier in soil mechanics research, with many significant advances (e.g., Bishop 1959; Matyas [...]

Dynamic compaction is commonly used to construct structural fills for various geo-infrastructures. Current practice is to specify a minimum dry density and moisture content criterion to be used in the field on the basis of Proctor compaction carried out in the laboratory. However, there are still no practical methods for predicting compacted clay behaviour under expected mechanical and environmental loadings. Current theories are difficult to apply in practice due to difficulties in determining the necessary parameters. In this paper, the recently developed 'void ratio--moisture ratio (volume of water / volume of solids)--net stress space' (MPK) framework is extended to cover dynamically compacted soils, with significant supporting experimental evidence. Two types of soils are used: lightly reactive kaolin and reactive Merri Creek clay. As the compaction stress was unknown for dynamic compaction, recompression of soil specimens from compacted soil was used to establish the 'loading wetting state boundary surface' (LWSBS). Independent tests show that the framework can predict well the behaviour of compacted soils under loading- unloading and yielding, collapse during wetting, change of loading yield stress after wetting, and swelling pressure development during constrained wetting. The value of the approach is that the testing methods are straightforward, do not require specialized equipment, and testing times are much shorter. In addition, the uncertainty that laboratory dynamic compaction may not relate directly to field roller compaction can be addressed with the developed framework. Soil specimens obtained from field soil pads compacted by actual rollers can be used to establish the LWSBS. This information will allow prediction of the likely behaviour of field-compacted fills under expected environmental and mechanical loadings subject to one-dimensional conditions. Extension to triaxial conditions would require further experimental work and theoretical modelling. Key words: dynamic compaction, wetting collapse, Proctor test, void ratio-- moisture ratio--net stress space (MPK) framework, compacted fills. Le compactage dynamique est couramment utilise pour realiser des remblais structuraux dans le cadre de travaux de construction de diverses geoinfrastructures. La pratique actuelle consiste a specifier une densite seche minimale et une valeur standard de teneur en eau destinees a etre utilisees sur le terrain en se basant sur les essais de compactage Proctor effectues en laboratoire. Cependant, nous ne disposons toujours pas de methodes pratiques permettant de predire le comportement d'une argile compactee soumise a des contraintes mecaniques et environnementales connues a l'avance. Les theories actuelles sont difficiles a mettre en pratique, en raison de la difficulte a determiner les parametres necessaires. Dans le present article, le champ d'application de la methode pratique utilisant l'indice des vides, le coefficient d'humidite et les contraintes nettes (MPK) recemment mise au point est etendu aux sols soumis a un compactage dynamique grace a des preuves experimentales solides. Deux types de sols sont utilises : un sol compose de kaolin legerement reactif et une argile reactive de Merri Creek. Etant donne que la contrainte de compactage etait inconnue dans le cas du compactage dynamique, on a eu recours a la recompression de specimens provenant d'un sol compacte pour determiner la surface limite des etats d'un sol soumis a une humidification ou a un chargement (SLEHC). Des essais realises separement ont montre que la methode MPK pouvait permettre de correctement predire le comportement de sols compactes soumis a un chargement ou une decompression et a une contrainte de rupture, a un effondrement pendant l'humidification, aux variations de la contrainte de chargement et de rupture apres humidification et a l'augmentation de la pression de gonflement durant l'humidification forcee. L'avantage de l'approche adoptee est que les methodes d'essai sont simples, qu'elles ne necessitent pas l'utilisation d'un equipement specialise et que la duree des essais est tres courte. En outre, grace a la methode elaboree, il est possible de verifier s'il existe veritablement un lien direct entre le compactage dynamique en laboratoire et le compactage au rouleau compresseur effectue sur le terrain. Les specimens de sol obtenus a partir des blocs de sol compactes sur le terrain par des rouleaux compresseurs peuvent servir a determiner la SLEHC. Cette derniere permettra de predire le comportement probable de remblais compactes sur le terrain et soumis a des contraintes environnementales et mecaniques connues a l'avance dans des conditions unidimensionnelles. Pour pouvoir etendre cette methode a des conditions triaxiales, il faudrait recourir a des experiences et des modeles theoriques plus approfondis. [Traduit par la Redaction] Mots-cles : compactage dynamique, effondrement par humidification, essai Proctor, methode pratique utilisant l'indice des vides, le coefficient d'humidite et les contraintes nettes (MPK), remblais compactes., Introduction Dynamic compaction is commonly used to undertake earthworks in civil engineering. It is carried out in the field using various forms of rollers to impart mechanical energy into soil [...]

Reactive magnesia (MgO)-activated ground granulated blastfurnace slag (GGBS), with fixed GGBS dosages but varying MgO/GGBS ratios, was used for stabilization of two soils and compared with brucite (Mg[(OH).sub.2])-activated GGBS and hydrated lime (Ca[(OH).sub.2])-activated GGBS. A range of tests, including unconfined compressive strength testing, X-ray diffraction, and scanning electron microscopy, was conducted to study the mechanical, chemical, and microstructural properties of the stabilized soils, and then to investigate the mechanism of MgO-GGBS soil stabilization. Results indicate that the Mg[(OH).sub.2] had a minimal activating efficacy for GGBS-stabilized soil, while the reactive MgO yielded a higher activating efficacy than the Ca[(OH).sub.2]. The activator-soil reactions in the stabilized soil slowed down the activating reaction rate for GGBS; this effect was less significant in MgO-GGBS-stabilized soil than in Ca[(OH).sub.2]-GGBS-stabilized soil, and hence the GGBS hydration rate in the former was less reduced by the soil than the latter. The [Mg.sup.2+] and OH- ions produced from MgO dissolution participated in the GGBS hydration reactions without precipitating Mg[(OH).sub.2]. The common hydration products in all GGBS- stabilized soils were calcium silicate hydrate-like compounds. Additionally, hydrotalcite and calcite could be produced in MgO-GGBS- and Ca[(OH).sub.2]-GGBSstabilized soils, respectively, especially with a high activator/GGBS ratio. Key words: soil stabilization, ground granulated blastfurnace slag (GGBS), magnesia, brucite, lime. Du laitier de haut-fourneau granule broye (LHGB) active par de la magnesie reactive (MgO), contenant des doses fixes de LHGB et des ratios variables MgO/LHGB, a servi a stabiliser deux sols et a ete compare avec du LHGB active par de la brucite (Mg[(OH).sub.2]) et du LHGB active par de la chaux eteinte (Ca[(OH).sub.2]). Une serie d'essais, comprenant un essai de resistance a la compression non confinee et des analyses par diffraction des rayons X et par microscopie electronique a balayage, ont permis d'etudier les proprietes mecaniques, chimiques et microstructurales des sols stabilises, puis d'analyser le mecanisme de stabilisation des sols au moyen de LHGB active par de la magnesie reactive. Les resultats ont montre que la brucite presentait une efficacite d'activation minimale dans le cas d'un sol stabilise a l'aide de LHGB et que l'efficacite d'activation de la magnesie reactive etait plus elevee que celle de la chaux eteinte. Les reactions entre le sol et l'agent d'activation dans le sol stabilise ont eu pour effet de ralentir la reaction d'activation du LHGB. Cet effet etait moins important dans le cas du sol stabilise a l'aide de LHGB active par de la magnesie reactive que dans celui du sol stabilise au moyen de LHGB active par de la chaux eteinte. Ainsi, la vitesse de la reaction d'hydratation du LHGB dans le premier cas etait moins reduite sous l'action du sol que dans le second cas. Les ions [Mg.sup.2+] et OH- liberes lors de la dissolution de la magnesie reactive ont participe aux reactions d'hydratation du LHGB sans causer la precipitation de la brucite. Les produits d'hydratation les plus souvent observes dans tous les sols stabilises a l'aide de LHGB etaient des composes de type silicate de calcium hydrate. En outre, il a ete possible de produire de l'hydrotalcite et de la calcite respectivement dans les sols stabilises a l'aide de LHGB active par de la magnesie reactive et dans ceux stabilises a l'aide de LHGB active par de la chaux eteinte, en particulier en presence d'un ratio eleve agent d'activation/LHGB. [Traduit par la Redaction] Mots-cles : stabilisation du sol, laitier de haut-fourneau granule broye (LHGB), magnesie, brucite, chaux., Introduction Chemical soil stabilization is one of the most widely used soil treatment methods, with lime (CaO and Ca[(OH).sub.2]) and Portland cement (PC) as the most commonly employed binders (e.g., [...]

The 'constant rate of strain' consolidation test has been widely used for several decades to provide a continuous load-displacement response. An exact theoretical solution can be obtained for this consolidation problem. Two other solution techniques have pedagogic advantage in their simplicity, and in their ability to (i) clarify the phases of response of the consolidating sample and (ii) be extended to incorporate additional details of material response or testing configuration. The parabolic isochrone technique imposes a particular mode shape on the isochrones at all times. Treating the sample as a single system, and applying the boundary conditions at the system level, the governing equation becomes an ordinary differential equation. For more elaborate soil properties or experimental procedures a finite difference description of the problem is readily programmed and solved. These solution techniques are used to illustrate the importance of distinguishing between the observed response of the system--the soil specimen under test--and the behaviour of the soil elements that make up this system. Examples are given of erroneous conclusions that might be drawn if this distinction is not recognised. Key words: consolidation, analysis, isochrones, constant rate of strain, seepage. Les essais de consolidation a << vitesse de deformation constante >> ont ete largement utilises pendant des decennies pour fournir une courbe continue representant le deplacement observe en fonction du chargement applique. Dans le cas de l'analyse de la consolidation a vitesse de deformation constante, une solution theorique exacte peut etre obtenue. Deux autres methodes de resolution du probleme ont un avantage pedagogique en raison de leur simplicite, leur capacite a clarifier les phases de reponse de l'echantillon de consolidation et leur capacite a avoir un champ d'application plus large en integrant des details supplementaires lies a la reponse materielle ou a la configuration des essais. La technique des isochrones paraboliques impose une forme modale particuliere aux isochrones en tout temps. Si l'on considere l'echantillon comme un systeme simple et que l'on applique les conditions limites a l'echelle du systeme, l'equation principale devient alors une equation differentielle ordinaire. Dans le cas de proprietes de sol ou de procedures experimentales plus complexes, une description du probleme a l'aide de la methode des differences finies est facilement programmee et resolu. Ces methodes de resolution servent a demontrer l'importance de faire la distinction entre la reponse du systeme observee (specimen de sol soumis aux essais) et le comportement des elements de sol qui constituent ce meme systeme. On fournit egalement des exemples de conclusions erronees que l'on peut tirer si cette distinction n'est pas admise. [Traduit par la Redaction] Mots-cles : consolidation, analyse, isochrones, infiltration, vitesse constante de deformation., Introduction Different configurations of consolidation test are used for the determination of flow and deformation properties of soil. The standard incremental loading test produces a well-known analytical solution, but this [...]

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

A reactive magnesia (MgO) was used to stabilize a natural soil; the MgO-stabilized soil was subjected to forced carbonation with pressurized gaseous C[O.sub.2] in a triaxial cell set-up. The change of physical properties, including bulk density, moisture content, dry density, specific gravity, and porosity, of the stabilized soil during carbonation was studied. The mechanical and microstructural properties of the carbonated MgO-stabilized soil were also investigated through unconfined compressive strength (UCS) test, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The results indicated that the carbonation of MgO-stabilized soil consumed C[O.sub.2] and water, and produced expansive carbonation products; this consequently increased the dry density, and reduced the moisture content, specific gravity, and porosity of the stabilized soil. After being carbonated for only 1.5 h, the MgO-stabilized soil yielded remarkable strength, with UCS higher than that of the 28 day ambient cured Portland cement-stabilized soil, mainly due to the high binding effect of carbonation products and the low porosity of carbonated MgO-stabilized soil. The carbonated MgO-stabilized soil achieved a high degree of carbonation in a few hours (≤ 12 h), with the maximum C[O.sub.2]/MgO ratio in a range of 0.76-1.07. Key words: soil stabilization, magnesia, carbonation, property, change. Dans la presente etude, on a stabilise un sol naturel a l'aide de magnesie (MgO). Le sol ainsi stabilise a ete ensuite soumis a une carbonatation forcee au moyen de C[O.sub.2] gazeux sous pression a l'interieur d'une cellule triaxiale. On a etudie les modifications des proprietes physiques du sol stabilise, notamment la densite apparente, la teneur en eau, la densite seche, la densite relative et la porosite, durant la carbonatation. On a egalement analyse les proprietes mecaniques et microstructurales du sol stabilise a l'aide de magnesie et carbonate en effectuant un essai de resistance a la compression non confinee (RCNC), une analyse diffractometrique aux rayons X, une analyse au microscope electronique a balayage (MEB) et des mesures au porosimetre a mercure. Les resultats ont montre que la carbonatation d'un sol stabilise a l'aide de magnesie consommait du C[O.sub.2] et de l'eau et liberait de nombreux types de produits. Cela a entraine une augmentation de la densite seche et une diminution de la teneur en eau, de la densite relative et de la porosite du sol stabilise. Apres avoir subi une carbonatation d'une heure et demie seulement, le sol stabilise avec de la magnesie presentait une resistance exceptionnellement elevee et une RCNC superieure a celle d'un sol stabilise a l'aide de ciment Portland durci a l'air ambiant durant 28 jours. Cela est principalement du au fort pouvoir liant des produits de la carbonatation et a la faible porosite du sol stabilise a l'aide de magnesie et carbone. Ce dernier a subi une forte carbonatation en quelques heures (≤ 12 h), la valeur maximale du rapport C[O.sub.2]/MgO etant comprise entre 0,76 et 1,07. [Traduit par la Redaction] Mots-cles: stabilisation du sol, magnesie, carbonatation, propriete, modification., Introduction Cement soil stabilization is a widely employed technique for geotechnical engineering applications (e.g., Sherwood 1993; Bergado et al. 1996; Al-Tabbaa 2003; Puppala et al. 2003; Chew et al. 2004; [...]

Seepage-induced internal erosion often happens in earth structures. This paper presents experimental investigations on the influence of initial fines content on fabric of soils subjected to internal erosion. The tested materials were the binary mixtures of silica No. 3 and silica No. 8, which correspond to the coarse and fine fractions, respectively. One group of specimens was prepared with initial fines contents of 0,15%, 25%, and 35% by weight. The undrained monotonic compression tests were performed on this group to examine the influence of fines content on the undrained behavior. The other group was prepared with initial fines contents of 15%, 25%, and 35% by weight, on which the seepage tests and subsequent undrained compression tests were carried out to demonstrate the mechanical influence of the internal erosion. The undrained behavior of the first group of specimens reveals that the presence of fines would decrease the peak and residual strengths. A comparison between the undrained behavior of soils with erosion and that of soils without erosion shows that the soils become less contractive after the internal erosion. When the axial strain is less than 0.4%, the undrained secant stiffness of soils with erosion is larger than that without erosion at the same axial strain. Meanwhile, the undrained peak strength and residual strength are larger for soils with erosion than that for soils without erosion. The less amount of excess pore-water pressure is generated during the undrained compression for the eroded soils comparing to those of the uneroded soils. Furthermore, the eroded soils show a wider instability zone than that of the uneroded soils, which suggests that the instability zone be enlarged by the internal erosion. Besides, one-dimensional upward seepage tests were performed to investigate the change of fabric of the mixed sand with 15%, 25%, and 35% fines contents due to internal erosion. The recorded microscopic images ofsoils before and after erosion reveal that the fabric is altered by the internal erosion. Key words: fines content, internal erosion, undrained compression, soil strength. La structure des sols subit souvent un phenomene d'erosion interne en raison de l'infiltration d'eau. Le present article decrit des etudes experimentales portant sur l'influence de la teneur initiale en particules fines de sols subissant une erosion interne sur la microstructure de ces derniers. Les essais realises ont ete realises sur des melanges composes de silice de types no. 3 et no. 8, correspondant respectivement a des particules de grande taille et a des particules fines. Le premier groupe etait forme de specimens ayant des teneurs initiales en particules fines de 0,15, 25 et 35 % de leur poids. On a effectue des essais de compression monotone non drainee sur ce groupe afin d'etudier l'influence de la teneur en particules fines sur le comportement non draine. Dans le second groupe, les teneurs initiales en particules fines etaient de 15, 25 et 35 % en poids. On a soumis les specimens de ce groupe a des essais d'infiltration puis a des essais de compression non drainee pour montrer l'influence mecanique de l'erosion interne. Le comportement non draine du premier groupe de specimens revele que la presence de particules fines aurait pour effet de diminuer la resistance de pointe et la resistance residuelle du sol. En comparant le comportement non draine des sols subissant une erosion a celui des sols non soumis a l'erosion, on constate que les sols se contractent moins apres avoir subi une erosion interne. Lorsque les contraintes axiales sont inferieures a 0,4 %, la rigidite secante non drainee des sols soumis a une erosion est superieure a celle des sols ne subissant pas d'erosion a contraintes axiales egales. Parallelement, la resistance non drainee de pointe et la resistance non drainee residuelle des sols soumis a une erosion sont superieures a celles des sols ne subissant pas d'erosion. L'exces de pression interstitielle genere durant la compression non drainee est moins important dans le cas des sols erodes que dans celui des sols non erodes. Parailleurs, les sols erodes presententune zone d'instabilite plus large que celle des sols non erodes, ce qui indique que cette zone d'instabilite s'elargit sous l'effet de l'erosion interne. De plus, des essais unidimensionnels d'infiltration ascendante ont ete realises afin d'etudier la modification de la microstructure de melanges de sables contenant 15, 25 et 35 % de particules fines sous l'effet d'une erosion interne. Les images du sol obtenues au microscope avant et apres erosion montrent que sa microstructure est modifiee par l'erosion interne. [Traduit par la Redaction] Mots-cles: teneur en particules fines, erosion interne, compression non drainee, resistance du sol., Introduction Internal erosion is a subsequent transport of detached finer soil particles through the matrix under seepage flow. The initiation of internal erosion has been investigated in terms of the [...]

This paper presents results of a numerical modelling exercise that investigates the effects of hysteresis of the soil-water characteristic curve (SWCC) on the infiltration characteristics of soils subjected to four different climatic conditions--from very dry to wet--within the Canadian province of Alberta. Multi-year climate datasets from four different natural regions and subregions of Alberta are compiled, classified, and applied as the soil-atmosphere boundary condition in one- dimensional finite element unsaturated flow models using Hydrus-1D software. Multi-year simulations are carried out with and without consideration of the SWCC hysteresis. Simulation results are analyzed in terms of water balance at the ground surface and temporal distribution and storage of water within the soil domain. It is demonstrated that hysteresis of the SWCC can significantly affect the prediction of flow, redistribution, and storage of water in the unsaturated zone. It is found that for soils that exhibit hysteretic SWCC, consideration of hysteresis in unsaturated flow modelling results in the prediction of lower infiltration and less movement of water through the soil. It is also found that the use of wetting parameters results in the prediction of increased infiltration and movement of water compared with the predictions using drying or hysteretic parameters. It is concluded that, for soils that exhibit a greater degree of SWCC hysteresis, it is important to measure both the drying and wetting branches of the SWCC accurately and that accurate simulation of hysteretic behaviour requires climate datasets at appropriate resolution. The results presented in this paper highlight the importance of considering SWCC hysteresis for a wide range of geotechnical problems, such as soil cover design, prediction of groundwater recharge, contaminant transport through unsaturated soils, soil erosion, slope stability, and swelling-shrinkage of expansive soils. Key words: unsaturated flow, soil-water characteristic curve, hysteresis, climate conditions, numerical modelling, infiltration, surface run-off, moisture movement. Le present article decrit les resultats d'une modelisation numerique permettant d'etudier l'effet de l'hysteresis de la courbe caracteristique sol-eau (CCSE) sur les mecanismes d'infiltration d'eau dans des sols soumis aux quatre climats differents (tres sec a humide) qui caracterisent la province canadienne de l'Alberta. Des series de donnees recueillies sur plusieurs annees dans quatre regions et sous-regions naturelles de l'Alberta ont ete rassemblees et classees et ont servi de conditions limites dans le cadre de modelisations unidimensionnelles d'ecoulement non sature par elements finis realisees a l'aide du logiciel Hydrus-1D. On a effectue des simulations a l'echelle de plusieurs annees en prenant compte ou non l'hysteresis de la CCSE. On a analyse les resultats de ces simulations en examinant l'equilibre hydrique ainsi que la distribution temporelle de l'eau et les reserves en eau dans le sol. On a montre que l'hysteresis de la CCSE pouvait beaucoup influer sur la prediction de l'ecoulement et de la redistribution de l'eau et des reserves en eau dans la zone non saturee. On a constate que, dans le cas des sols dont la CCSE est hysteretique, lorsque l'on prend en compte de l'hysteresis lors de la modelisation de l'ecoulement insature, on predit une infiltration et des mouvements d'eau dans le sol moins importants. On a egalement remarque que, lorsqu'on utilisait les parametres de mouillage, on predisait une infiltration et des deplacements d'eau plus importants que ceux predits a l'aide des parametres de sechage. On en a conclu que, dans le cas de sols caracterises par une CCSE fortement hysteretique, il etait important de calculer precisement a la fois la portion de la CCSE correspondant au sechage et celle associee au mouillage et que, pour simuler avec precision l'hysteresis, il etait necessaire de disposer de series de donnees climatiques de resolution appropriee. Les resultats presentes dans cet article montrent qu'il est important de prendre en compte l'hysteresis de la CCSE dans le cadre de nombreux problemes geotechniques, tels que la conception de sols de couverture, la prediction de la recharge des nappes phreatiques, le transport des contaminants dans les sols non satures, l'erosion du sol, la stabilite des terrains en pente et le gonflement ou la contraction des sols gonflants. [Traduit par la Redaction]. Mots-cles : ecoulement non sature, courbe caracteristique sol-eau, hysteresis, conditions climatiques, modelisation numerique, infiltration, ecoulement de surface, deplacement d'humidite., Introduction Problems involving groundwater flow through unsaturated soils are often analyzed using numerical models. These models require reliable input data for the soil's hydraulic functions for accurate analysis of such [...]

Shear wave velocity, [V.sub.s], is a soil mechanical property that can be advantageously measured in both the field and laboratory under real and controlled conditions. The measured [V.sub.s] values are customarily used in conjunction with other in situ (e.g., standard penetration test blow count, N-SPT, and cone penetration resistance, [q.sub.c]-CPT) and laboratory (e.g., effective confining pressure, [σ'.sub.m], and void ratio, e) measurements to establish an abundant number of [V.sub.s]- based correlations that could later be utilized to augment (in some cases, replace) designated testing. An attempt is made here to present the salient features of some existing widely used correlations to provide the reader with a comprehensive understanding about the nature of these correlations and their applicability in geotechnical engineering practices. It is recognized that the reliability of some of these empirical formulations, still in general use today, has been questioned, as they are characterized by their lack of dependence on stress state and particle characteristics. A new [V.sub.s1]-[([N.sub.1]).sub.60] (where [V.sub.s1] is the stress- normalized shear wave velocity, and [([N.sub.1]).sub.60] is the stress-normalized penetration blow count) correlation that accounts for grain sizes is highlighted by combining a recently published [V.sub.s1]-[q.sub.c1] (where [q.sub.c1] is the stress-normalized cone tip resistance) formulation and available [([N.sub.1]).sub.60]-[q.sub.c1] relationships. The new formulation is applicable to uncemented relatively young Holocene-age soil deposits. The estimated [V.sub.s1] values based on the proposed correlation are compared with reliable laboratory and field measurements, and the comparison shows that accounting for grain size of granular soils yields more realistic results regarding the [V.sub.s] values than when particle size is not considered. The prime effect of grain size was to change the range of possible void ratios, which in turn had a substantial impact on [V.sub.s] values. Moreover, a new [V.sub.s1]-[([N.sub.1]).sub.60] chart has been proposed, allowing the practitioner to estimate [V.sub.s1] values based on a combination of data including N-SPT, e, grain size, and relative density. Key words: shear wave velocity, grain size, standard penetration test (SPT), piezocone cone penetration test (CPTu), soil density index ([I.sub.d]), correlation. La vitesse des ondes de cisaillement, [V.sub.s], est une propriete mecanique des sols qui a l'avantage de pouvoir etre mesuree a la fois sur le terrain et en laboratoire, dans des conditions reelles ou controlees. Les valeurs mesurees de [V.sub.s] sont souvent utilisees en association avec d'autres grandeurs mesurees en place (p. ex. le nombre de coups lors de l'essai de penetration standard, N-SPT, et la resistance a la penetration du cone, [q.sub.c]-CPT) et en laboratoire (p. ex. la pression effective de confinement, [σ'.sub.m], et l'indice des vides, e) afin d'etablir un grand nombre de correlations peuvent etre utilisees ulterieurement pour multiplier (et, dans certains cas, remplace) des essais specifiques. Dans le present article, on essaie de presenter les principales caracteristiques de certaines correlations largement utilisees, afin de permettre au lecteur de comprendre la nature de ces correlations et leur applicabilite dans le domaine de la geotechnique. On admet que la fiabilite de certaines de ces relations empiriques, encore tres utilisees de nos jours, peut etre remise en doute etant donne qu'elles ne tiennent pas compte de l'etat des contraintes et des caracteristiques granulometrique du sol. Une nouvelle correlation entre [V.sub.s1] et [([N.sub.1]).sub.60] (ou [V.sub.s1] est la vitesse de l'onde de cisaillement normalisee et [([N.sub.1]).sub.60] est le le nombre de coups de battage lors d'un essai de penetration normalise) qui tient compte de la taille des grains, est etablie par combinaison d'une formule recemment publiee et basee sur [V.sub.s1] et [q.sub.c1] (ou [q.sub.c1] est la resistance en pointe normalisee) et de relations existantes entre [([N.sub.1]).sub.60] et [q.sub.c1]. Cette nouvelle correlation peut s'appliquer a des depots de sol non consolides relativement jeunes, datant de l'holocene. Les valeurs de [V.sub.s1] estimees et basees sur la correlation proposee sont comparees a des mesures fiables effectuees en laboratoire et sur le terrain et la comparaison montre que la prise en compte de la taille des grains constituant les sols granulaires permet d'obtenir des valeurs de [V.sub.s] plus realistes par rapport a celles obtenues sans que l'on tienne compte de la taille des particules. La taille des grains a principalement pour effet de modifier les valeurs possibles de l'indice des vides, lequel influe lui-meme beaucoup sur les valeurs de [V.sub.s]. En outre, une nouvelle charte representant la relation entre [V.sub.s1] et [([N.sub.1]).sub.60] est propose, qui permet aux utilisateurs d'estimer les valeurs de [V.sub.s1] en combinant des donnees telles que N-SPT, e, la taille des grains et la densite relative. [Traduit par la Redaction] Mots-cles : vitesse des ondes de cisaillement, taille des grains, essai de penetration normalise (SPT), essai de penetration au piezocone (CPTu), indice de densite du sol ([I.sub.d]), correlation., Introduction It is essential to properly estimate shear wave velocity, [V.sub.s], of granular soils at strain levels less than [10.sup.-3]%, as its relevance for the analysis and design of various [...]

This paper proposes a new, integrated two-layer model to capture nonlinear response of rotationally restrained laterally loaded rigid piles subjected to soil movement (sliding soil, or lateral spreading). First, typical pile response from model tests (using an inverse triangular loading profile) is presented, which includes profiles of ultimate on-pile force per unit length at typical sliding depths, and the evolution of pile deflection, rotation, and bending moment with soil movement. Second, a new model and closed-form expressions are developed for rotationally restrained passive piles in two-layer soil, subjected to various movement profiles. Third, the solutions are used to examine the impact of the rotational restraint on nonlinear response of bending moment, shear force, on-pile force per unit length, and pile deflection. Finally, they are compared with measured response of model piles in sliding soil, or subjected to lateral spreading, and that of an in situ test pile in moving soil. The study indicates the following: (i) nonlinear response of rigid passive piles is owing to elastic pile-soil interaction with a progressive increase in sliding depth, whether in sliding soil or subjected to lateral spreading; (ii) theoretical solutions for a uniform movement can be used to model other soil movement profiles upon using a modification factor in the movement and its depth; and (iii) a triangular and a uniform pressure profile on piles are theoretically deduced along lightly head-restrained, floating-base piles, and restrained-base piles, respectively, once subjected to lateral spreading. Nonlinear response of an in situ test pile in sliding soil and a model pile subjected to lateral spreading is elaborated to highlight the use and the advantages of the proposed solutions, along with the ranges of four design parameters deduced from 10 test piles. Key words: passive piles, analytical solutions, nonlinear response, soil-structure interaction. Cet article propose un nouveau modele a deux couches integrees servant a representer le comportement non lineaire de pieux rigides charges lateralement et dont la rotation est restreinte, dans des conditions de mouvements de sol (glissement ou etalement lateral). D'abord, la reponse typique d'un pieu obtenue a partir d'essais modeles (avec un profil de charge triangulaire inversee) est presentee, incluant les profils de la force ultime sur le pieu par unite de longueur pour des profondeurs de glissement typiques, et revolution de la deflection, de la rotation et du moment de torsion du pieu selon les mouvements du sol. Ensuite, un nouveau modele et des expressions a forme fermee sont developpes pour des pieux passifs restreints en rotation dans un sol a deux couches soumis a differents profils de mouvement. Troisiemement, les solutions sont utilisees pour etudier l'impact de la restriction en rotation sur la reponse non lineaire du moment de torsion, de la force de cisaillement, de la force sur le pieu par unite de longueur, et la deflection du pieu. Finalement, ces solutions sont comparees avec la reponse mesuree de pieux modeles dans un sol glissant, ou sujet a l'etalement lateral, et celle d'un pieu d'essai in situ dans un sol en mouvement. L'etude indique que (i) la reponse non lineaire de pieux passifs rigides depend de l'interaction elastique sol-pieu avec une augmentation progressive selon la profondeur de glissement, autant dans les sols glissants que dans les sols sujets a l'etalement lateral; (ii) les solutions theoriques d'un mouvement uniforme peuvent etre utilisees pour modeliser d'autres profils de mouvement de sol si l'on utilise un facteur de modification pour le mouvement et pour sa profondeur; et (iii) des profils de pression triangulaire et uniforme sur les pieux sont deduits theoriquement le long de pieux restreints a la tete, a base flottante, et restreints a la base, respectivement, une fois soumis a l'etalement lateral. La reponse non lineaire d'un pieu d'essai in situ dans un sol glissant et d'un pieu modele soumis a l'etalement lateral est elaboree afin de mettre en evidence l'utilisation et les avantages des solutions proposees, ainsi que les valeurs de quatre parametres de conception deduits de 10 essais de pieux. [Traduit par la Redaction] Mots-cles: pieux passifs, solutions analytiques, reponse non lineaire, interaction sol-structure., Introduction Passive piles are known as piles that are subjected to soil movement and are commonly used for stabilising a sliding slope, supporting bridge abutments, and providing a lateral pressure [...]

Given extensive research carried out to study pile response subjected to lateral soil movement in clay, the effect of consolidation on the pile--soil interaction is rarely considered and systematically investigated. For this reason, four centrifuge tests were conducted to simulate construction of embankment adjacent to existing single piles in soft clay, considering two typical drainage conditions (i.e., drained and undrained conditions) and two typical pile lengths (i.e., relatively long pile and short pile). The centrifuge tests were then back-analyzed by three-dimensional coupled-consolidation finite element analyses. Based on reasonable agreements between the two, numerical parametric studies were conducted to systematically investigate and quantify the influence of construction rate and pile length on pile response. It is revealed that by varying drainage conditions, the piles respond distinctively. When the embankment is completed within a relatively short period ([c.sub.v]t/[d.sup.2] < 2, where [c.sub.v], t, and d denote the coefficient of consolidation, construction period, and pile diameter, respectively), the pile located adjacent to it deforms laterally away from the embankment. Induced lateral pile deflection ([delta]) and bending moment reduce with construction period. On the contrary, embankment constructed within a relatively long period (c[v.sub.t]/[d.sup.2] > 200) leads the pile to deform laterally towards the embankment, with [delta] and bending moment increases with construction period. By halving the length of pile embedded in the drained ground, the maximum induced bending moment ([BM.sub.max]) was slightly reduced (by 23%). On the other hand, shortening the length of the pile in the undrained ground is much more effective in reducing [BM.sub.max,] i.e., halving pile length resulting in 78% reduction in bending moment. A new calculation chart, which takes various drainage conditions and pile lengths into account, was developed for estimation of [BM.sub.max]. Key words: centrifuge modelling, finite element analysis, hypoplastic model, pile, soft clay, consolidation. Malgre les nombreuses recherches sur le comportement des pieux soumis fi des mouvements de sol lateraux dans l'argile, l'effet de la consolidation sur l'interaction pieu-sol est rarement considere, ni evalue systematiquement. Pour cette raison, quatre essais en centrifugeuse ont ete realises pour simuler la construction d'un remblai adjacent a des pieux simples dans de l'argile molle, en considerant deux conditions typiques de drainage (conditions drainee et non drainee) et deux longueurs de pieu typiques (pieux relativement long et court). Les essais en centrifugeuse ont ensuite ete retro-analyses a l'aide d'analyses par elements finis en trois dimensions de consolidation couplee. Base sur un accord raisonnable entre les deux, des etudes parametriques numeriques ont ete realisees pour etudier systematiquement, de meme que quantifier, l'influence du taux de construction et de la longueur du pieu sur le comportement du pieu. Il est demontre qu'en variant les conditions de drainage, le pieu repond differemment. Lorsque le remblai est complete dans une periode relativement courte ([c.sub.v]t/[d.sup.2] < 2, ou [c.sub.v], t et d representent le coefficient de consolidation, la periode de construction et le diametre du pieu, respectivement), le pieu adjacent se deforme lateralement a l'oppose du remblai. La deflection laterale du pieu induite ([delta]) et le moment de torsion sont reduites selon la periode de construction. Au contraire, un remblai construit sur une periode relativement longue ([c.sub.v] t/[d.sup.2] > 200) cause une deformation laterale du pieu en direction du remblai, et [delta] et le moment de torsion augmentent selon la periode de construction. En reduisant de moitie la longueur du pieu enfouie dans le sol draine, le moment de torsion maximum induit ([BM.sub.max]) est legerement reduit (de 23 %). D'un autre cote, la reduction de longueur d'un pieu dans un sol non draine est beaucoup plus efficace a reduire [BM.sub.max], en effet une reduction de moitie reduit de 78 % le moment de torsion. Une nouvelle charte de calcul, qui tient compte des differentes conditions de drainage et de longueurs de pieux, a ete developpee pour estimer [BM.sub.max]. [Traduit par la Redaction] Mots-cles: modelisation par centrifugeuse, analyse par elements finis, modele hypoplastique, pieu, argile molle, consolidation., Introduction Construction of an embankment on soft clay would inevitably induce soil lateral movement, which could possibly impose adverse effects on adjacent existing underground structures, such as piles. Under such [...]

In a number of practical cases, a typical one being the investigation of the subsoil properties below roads or foundations, one faces the problem of measuring the elastic properties of a geological layer (here called 'hidden layer') underlying a more compact and rigid surface layer. In such cases, the effectiveness of common surface seismic methods is poor for different reasons, but mostly linked to the reflection--transmission properties of the waves at a stiff-to-soft interface. Borehole methods are more efficient, but expensive and only provide vertical information at certain points. Attempts carried out in the past to characterize the hidden layer properties through surface seismic techniques consisted in placing the seismic source on the surface alongside, but off the stiff artificial layer (road or foundation). An alternative approach is presented based on placing the seismic source just below the stiff artificial layer. In cases where soil improvement--compaction are carried out through injection of expanding resins, then the hidden layer can be easily reached via the injecting tools and in some cases (e.g., urban settings characterized by laterally continuous artificial layers or roads constructed on embankments) this can be the only viable option. The results obtained from this approach using a number of practical cases where roads affected by differential sinking have later been compacted will be presented. The average soil improvement that can be achieved with the specific kind of expanding resin used in this study is then quantified. Key words: surface wave methods, soil improvement, resin injection. Dans un certain nombre de cas pratiques, parmi lesquels figure typiquement l'etude des proprietes du sous-sol des routes ou des fondations, on est confronte au probleme de la mesure des proprietes elastiques d'une couche geologique (nommee ici << couche cachee >>) situee sous une couche de surface plus compacte et plus rigide. Dans de tels cas, l'efficacite des methodes sismiques de surface traditionnelles est limitee pour differentes raisons et principalement liee aux proprietes de reflexion-transmission des ondes a l'interface d'une couche rigide et d'une couche molle. Les methodes consistant a creuser un trou de sonde sont plus efficaces mais plus cheres et ne fournissent que des donnees verticales en quelques points precis. Les tentatives entreprises dans le passe pour caracteriser les proprietes de la couche cachee a l'aide de techniques sismiques de surface consistaient a placer la source sismique sur la surface le long et en retrait de la couche artificielle rigide (route ou fondation). Une autre approche est presentee qui consiste a positionner la source sismique juste en dessous de la couche artificielle rigide. Dans les cas ou des operations d'amelioration-compactage du sol sont realisees par injection de resines expansibles, la couche cachee est facilement accessible fi l'aide d'outils d'injection et, dans certains cas (p. ex. configuration urbaine caracterisee par des couches artificielles continues laterales ou routes construites sur des remblais), il s'agit de la seule solution viable disponible. Les resultats obtenus a partir de cette approche et a l'aide de differents cas pratiques, dans lesquels les routes touchees par un affaissement differentiel ont ete compactees par la suite, seront presentes. L'amelioration globale du sol, amelioration realisee au moyen du type b specifique de resine expansible utilise dans la presente etude sera ensuite mesuree. [Traduit par la Redaction] Mots-cles: methodes des ondes de surface, amelioration du sol, injection de resine., Introduction In practical applications of civil engineering one of the main interests is in measuring the elastic parameters of the subsoil. In this work, the focus of attention is on [...]

With the rapid growth of the helical piling industry for oil and gas projects and transmission lines, reliable installation torque estimates and measurements become crucial. This paper presents a theoretical model developed to estimate the torsional resistance of cohesionless soils to helical pile installation. The theoretical torque model was verified using installation records collected from different sites. The paper also highlights factors that affect helical pile installation, including soil properties, fluctuation in groundwater levels, shape of pile shaft, pile geometry, and method of helical pile installation. The proposed torsional resistance model was then used to establish the traditional torque factors to proportionally correlate the axial capacity of helical pile and the installation torque. The results of the study indicated that the torque factor is a function of the load path (i.e., tension or compression). Therefore, torque factors in compression and tension, [K.sub.c] and [K.sub.t], respectively, were formulated and presented in the paper. Key words: helical piles, screw piles, torque, capacity, cohesionless, sand, compression, tension. Etant donne le developpement rapide du secteur de production des pieux helicoidaux, utilises dans les projets petroliers et gaziers et dans l'installation de canalisations de transport, il devient essentiel de realiser des estimations et mesures fiables du couple d'installation de ces pieux. Le present article presente un modele theorique concu pour permettre d'estimer la resistance de torsion de sols non cohesifs a l'installation de pieux helicoidaux. Le modele theorique de couple a ete verifie a l'aide de donnees d'installation collectees sur differents site. L'article souligne egalement les facteurs qui influent sur l'installation de pieux helicoidaux, en particulier les proprietes du sol, les variations du niveau de la nappe phreatique, la forme du fut du pieu, la geometrie du pieu et la methode d'installation du pieu helicoidal. Le modele de resistance de torsion propose a ete ensuite utilise pour etablir les facteurs de couple traditionnels qui relient proportionnellement la capacite axiale du pieu helicoidal au couple d'installation. Les resultats de l'etude ont montre que le facteur de couple est fonction de la voie de contrainte (c.-a-d. de tension ou de compression). Ainsi, les facteurs de couple en compression et en tension, [K.sub.c] et [K.sub.t], respectivement, et leur equation sont presentes dans le present article. [Traduit par la Redaction] Mots-cles: pieux helicoidaux, pieux visses, couple, capacite, non cohesif, sable, compression, tension., Introduction The installation of an [alpha]-helical pile is typically accomplished in the field by applying torque to the pile shaft using a rotary motor connected to the pile head. A [...]

This paper presents a straightforward approach for modelling volume change behavior of expansive soils during wetting--drying cycles. The swelling--shrinkage strain of expansive soils induced by cyclic wetting and drying was decomposed with distinctive physical background into a reversible component, which shows a synchronous change with the cyclic change of suction, and an irreversible component, which is generated mainly in the early stage of the wetting--drying process. The mechanisms of the two swelling--shrinkage strain components can be well explained through the double-level structure of expansive soils and its evolution with mechanical and hydraulic loading. The reversible component originates from the reversible deformation behavior of aggregates, and primarily depends on current suction or water content. The irreversible component is associated with the irreversible change of macrostructure, reflecting the difference in soil structures at current state and the equilibrium state. A practical constitutive model was proposed for compacted expansive clays from a global and phenomenological perspective. The model parameters can be calibrated with observed macroscopic deformation behavior without measuring microstructural parameters. The performance of the presented model was validated by simulating cyclic suction-controlled tests as well as an alternately soaked and dried test with irregular amplitudes of suctions. Key words: expansive soils, volumetric behavior, swelling, shrinkage, model. Cet article presente une approche directe pour modeliser les variations de volume de sols expansifs durant des cycles de mouillage-sechage. La deformation causee par le gonflement-retrait des sols expansifs induite par les cycles de mouillagesechage a ete decomposee, selon des notions physiques, en une composante reversible qui demontre une variation synchrone avec les variations cycliques de succion, et une composante irreversible qui est generee principalement dans les premieres etapes du processus de mouillage-sechage. Les mecanismes des deux composantes de la deformation en gonflement-retrait peuvent etre bien expliques grace a la structure a deux niveaux des sols expansifs et par l'evolution de cette structure avec les charges mecaniques et hydrauliques. La composante reversible provient de la deformation reversible des agregats, et depend principalement de la succion presente et de la teneur en eau. La composante irreversible est associee avec les variations irreversibles de la macrostructure, refletant les differences dans les structures du sol fi l'etat present et a l'etat d'equilibre. Un modele constitutif pratique est propose pour les argiles expansives compactees base sur une perspective globale et phenomenologique. Les parametres du modele peuvent etre calibres avec les deformations macroscopiques observees sans mesurer les parametres microstructuraux. La performance du modele presente a ete validee en simulant des essais de succion cyclique controles de meme d'avec un essai alternant le mouillage et le sechage avec des amplitudes irregulieres de succion. [Traduit par la Redaction] Mots-cles : sols expansifs, comportement volumetrique, gonflement, retrait, modele., Introduction Expansive soils can exhibit large volume change from change in soil moisture. Under seasonal changes in climatic and environmental conditions, expansive soils in situ inevitably experience cyclic wetting--drying processes [...]