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The hydromechanical behavior of compacted clayey soils is significantly influenced by its microstructure. The microstructural void ratio is a key parameter that is strongly associated with the microstructural state. The objective of this study is to provide a practical and reliable estimation approach for predicting the evolution of the microstructural void ratio of compacted clay soils subjected to wetting and drying paths. In this paper, the microstructural evolution of 12 clayey soils was investigated quantitatively using the mercury intrusion porosimetry (MIP) results. Based on this study, a comprehensive criterion has been developed for identifying different pore populations of compacted clayey soils for interpreting the MIP results. The 'as-compacted state line' was proposed to estimate the initial microstructural void ratio of clayey soils at the as-compacted state. An incremental linear constitutive model was proposed for correlating the microstructural void ratio to the 'microstructural average skeleton stress' in compacted clayey soils following monotonic wetting and drying paths. The developed approach is validated by providing comparisons between the predicted and interpreted microstructural void ratios for all the examined soils. The proposed approach can be extended in constitutive modeling of the hydromechanical behavior of compacted clayey soils by incorporating explicitly the microstructural information. Key words: microstructure, compacted clayey soils, microstructural void ratio, microstructural average skeleton stress, mercury intrusion porosimetry (MIP) Le comportement hydromecanique des sols argileux compactes est fortement influence par leur microstructure. Le taux de vide microstructural est un parametre cle qui est fortement associe a l'etat microstructural. L'objectif de cette etude est de fournir une approche d'estimation pratique et fiable pour predire l'evolution du taux de vide microstructurel des sols argileux compactes soumis a des chemins de mouillage et de sechage. Dans cet article, l'evolution microstructurale de 12 sols argileux a ete etudiee quantitativement en utilisant les resultats de la porosimetrie par intrusion de mercure (PIM). Cette etude a permis de developper un critere complet pour identifier les differentes populations de pores des sols argileux compactes afin d'interpreter les resultats du PIM. La << ligne d'etat tel que compacte >> (ACSL) a ete proposee pour estimer le taux de vide microstructurel initial des sols argileux a l'etat tel que compacte. Un modele constitutif lineaire incrementiel a ete propose pour correler le taux de vide microstructurel a la << contrainte moyenne du squelette microstructurel >> dans les sols argileux compactes apres des parcours monotones de mouillage et de sechage. L'approche developpee est validee par des comparaisons entre les taux de vide microstructurels predits et interpretes pour tous les sols examines. L'approche proposee peut etre etendue a la modelisation constitutive du comportement hydromecanique des sols argileux compactes en incorporant explicitement les informations microstructurelles. [Traduit par la Redaction] Mots-cles : microstructure, argileux compactes, rapport de vide microstructural, contrainte moyenne du squelette microstructural, porosimetrie par intrusion de mercure (MIP), 1. Introduction It is widely recognized in the literature that the soil microstructure significantly influences the hydraulic and mechanical properties of compacted clayey soils. The pioneering studies linking the macroscopic [...]

This study investigates the pore-water pressure increase associated with rainfall intensity and duration on a coal ash embankment slope and its effect on the slope stability for safe disposal and storage of coal ash storage facilities (CASFs). Several worldwide incidents during the last decades have revealed that rainfall-induced reductions in matric suction can compromise CASF slope stability, necessitating innovative solutions that address the influence of the coupled interplay of hydromechanical factors. For this reason, the key objective of the study is directed toward evaluating the efficacy of covers with capillary barrier effects (CCBE) to improve the stability of coal ash embankments. A comprehensive analysis, involving SEEP/W and SLOPE/W for uncoupled evaluations and SIGMA/W and SLOPE/W for coupled assessments, was conducted to explore various CCBE configurations. These configurations included fine coal ash (FCA)/coarse coal ash (CCA), FCA/fine recycled asphalt (FRA)/coarse recycled asphalt (CRA), and multilayered systems. The study also examined the influence of density, along with varying rainfall intensities and durations. Numerical modeling results suggest superior performance of three-layer systems, especially the FCA/FRA/CRA configuration, in maintaining matric suction and increasing the slope factor of safety. The system effectively relocated the point of maximum displacement away from the slope toe, suggesting a potential mechanism for enhanced stability and prevention of toe displacement failures. In addition, the study found that the performance of loose coal ash slopes improved with the application of passive reinforcement. The summarized research highlights a sustainable waste-covering-waste approach, introducing controlled nonhomogeneity in slopes to improve their stability against environmental factors. [ABSTRACT FROM AUTHOR]

Shallow foundations are used in many scenarios to transmit the loads from the lightly loaded superstructures constructed on expansive soil slopes. Infiltration associated with rainfall and snow melt influence both the foundation and the expansive soil behavior, including its slope. However, several research studies that are available in the literature focus on only one of these challenges. The combined influence of infiltration on the performance of the foundation and the slope in cracked expansive soils has not received the attention it deserves in the literature. In this study, the combined performance is evaluated with the aid of a numerical method considering shallow foundations located on the top of an unsaturated expansive cracked surficial soil slope. The influence of the rainfall intensity, rainfall duration, foundation setback distance, and foundation loading on the foundation bearing capacity and slope stability were investigated. The numerical results of the study highlight that all the parameters have a significant impact on the foundation–slope failure mechanisms associated with different infiltration conditions. [ABSTRACT FROM AUTHOR]

In this paper, two artificial intelligence (AI) models (i.e., artificial neural networks (ANN) and multivariate adaptive regression splines (MARS)) were developed using cumulative percentiles from the grain-size distribution (GSD) curve as input information to predict the soil-water characteristic curve (SWCC). The importance of each input variable was testified using two different sensitivity analyses. The results show a strong correlation between the SWCC and GSD curves based on large volume of datasets. The ANN provides higher accuracy due to its unique structure; however, the MARS model facilitates in developing a regression equation that contributes to stable performance. The SWCC can be reliably predicted with the MARS regression equation using one data point from the GSD curve and bulk density information. Sensitivity analysis suggests that the prediction of the SWCC is also possible with a reasonable degree of accuracy by using single data point information from the GSD curve as an input variable. Finally, a novel AI aid design method is proposed by combining the MARS regression equation along with physico-empirical model and fitting equation that provides a rapid and reliable technique for predicting the SWCC of sands. Key words: soil-water characteristic curve, grain-size distribution, artificial neural network, multivariate adaptive regression splines, artificial intelligence (AI) aid design method. Le present rapport met au point deux modeles d'intelligence artificielle (IA) (c'est-a-dire des reseaux neuronaux artificiels (ANN) et des splines de regression adaptative multivariee (MARS)) a partir des percentiles cumulatifs de la courbe de distribution granulometrique (GSD) comme informations d'entree pour predire la courbe caracteristique sol-eau (SWCC). Le role de chaque variable d'entree a ete teste en utilisant deux analyses de sensibilite differentes. Les resultats ont permis d'etablir une forte correlation entre les courbes SWCC et GSD sur la base d'un grand nombre de donnees. Le reseau ANN fournit une plus grande precision en raison de sa structure unique; cependant, le modele MARS facilite le developpement d'une equation de regression qui contribue a une performance stable. Le SWCC peut etre predit de maniere fiable avec l'equation de regression MARS en utilisant un point de donnees de la courbe GSD et des informations sur la densite apparente. L'analyse de sensibilite suggere que la prediction de la SWCC est egalement possible avec un degre raisonnable de precision en utilisant un seul point de donnees de la courbe GSD comme variable d'entree. Enfin, une nouvelle methode de conception d'aide a l'IA est proposee en combinant l'equation de regression MARS avec un modele physico-empirique et une equation d'ajustement qui fournit une technique rapide et fiable pour predire la SWCC des sables. [Traduit par la Redaction] Mots-cles : courbe caracteristique sol-eau, distribution granulometrique, reseau neuronal artificiel, splines de regression adaptatives multivariees, methode de conception de l'aide a l'intelligence artificielle (IA)., Introduction The relationship between water content (i.e., gravimetric or volumetric) or degree of saturation and matric suction is widely referred to as the soil-water characteristic curve (SWCC) in the literature. [...]

Several of the geotechnical structures constructed with unsaturated soils undergo a large deformation prior to reaching failure conditions (e.g., progressive failure of a soil slope). During this process, the shear stress in soils typically increases initially and then reduces with an increase in the shear strain. The prediction of the stress-strain relationship is critical for reasonable interpretation of the mechanical behavior of those geo-structures that undergo large deformation. This paper introduces a model based on the disturbed state concept (DSC) to predict the variation of shear stress in unsaturated soils during the strain-softening process under consolidated drained triaxial compression condition. In this model, the apparent stress-strain relationship is formulated as a weighted average of a hyperbolic hardening response extending the pre-peak state stress-strain curve and a linear response extending the critical state stress-strain curve with an assumed disturbance function as the weight. The prediction procedure is described in detail and the proposed model is validated using several sets of published data on unsaturated soils varying from coarse- to fine-grained soils. Finally, a comprehensive error analysis is undertaken based on an index of agreement approach. Key words: unsaturated soil, matric suction, stress-strain relationship, strain-softening, disturbed state concept. Plusieurs des structures geotechniques construites avec des sols non satures subissent une grande deformation avant d'atteindre des conditions de defaillance (par exemple, defaillance progressive d'un talus en terre). Au cours de ce processus, la contrainte de cisaillement dans les sols augmente generalement dans un premier temps, puis diminue avec l'augmentation de la contrainte de cisaillement. La prediction de la relation contrainte-deformation est essentielle pour une interpretation raisonnable du comportement mecanique des geostructures qui subissent de grandes deformations. Cet article presente un modele base sur le concept d'etat perturbe (DSC) pour predire la variation de la contrainte de cisaillement dans les sols non satures pendant le processus de deformation amollissement dans des conditions de compression triaxiale drainee consolidee. Dans ce modele, la relation apparente contrainte-deformation est formulee comme une moyenne ponderee d'une reponse de durcissement hyperbolique prolongeant la courbe contrainte-deformation a l'etat de pre-crete et d'une reponse lineaire prolongeant la courbe contrainte-deformation a l'etat critique avec une fonction de perturbation supposee comme poids. La procedure de prediction est decrite en detail et le modele propose est valide a l'aide de plusieurs series de donnees publiees sur les sols non satures, allant des sols a grains grossiers aux sols a grains fins. Enfin, une analyse complete des erreurs est effectuee sur la base d'une approche fondee sur un indice d'accord. [Traduit par la Redaction] Mots-cles: sol non sature, succion matricielle, relation contrainte-deformation, deformation amollissement, concept d'etat perturbe., Introduction The shear stress increases rapidly during the initial stage of shearing in both saturated and unsaturated soils. However, in several scenarios, shear stress drops gradually from peak to a [...]

The soil–water characteristics curve (SWCC) that is typically measured from laboratory tests is fit using mathematical models that are based on capillary law and used along with the saturated soil properties for predicting the hydro-mechanical behavior of unsaturated soils. Such SWCC models are valid for coarse-grained soils. However, the same models are also extended for modeling the SWCC of fine-grained soils over suction range from 0 to 106 kPa with a correction function. Due to this reason, SWCC models with correction functions have limitations in rigorous analyses of complex thermo-hydro-mechanical-chemo (THMC) behaviors of unsaturated soils, especially in the high suction range. In the present study, a correction function is proposed for modeling the SWCC behavior using two widely models based on a theoretical framework extending the principles of thermodynamics. The relationships between the traditional and the proposed correction functions are discussed. Finally, comparisons are provided between the proposed and the traditional correction functions on the SWCC behavior to highlight their differences. In addition, the effects of temperature and salinity on the SWCC with correction functions are also summarized. The proposed correction function is a valuable tool for rigorous analyses and reliable prediction of the complex THMC behaviors of unsaturated soils. [ABSTRACT FROM AUTHOR]

A comprehensive experimental program was performed in order to understand the mechanical behavior of model piles associated with water infiltration in collapsible loess. Real-time measurements were recorded for pile head settlement, pile shaft friction, and pile base resistance, as well as for the soil behavior, including soil settlement, volumetric water content, and soil suction. The experimental results suggest that both the pile head settlement and pile base resistance increased with water infiltration. The linear pile axial force distribution gradually changed to a "D" shape, with the maximum pile axial force occurring in the middle instead of the end stage of water infiltration. Such behavior can be attributed to a reduction in the contribution of soil suction, degradation of the pile–soil interface shear strength, and settlement of the collapsible soil. In addition, a softening model was proposed by modifying the traditional shear displacement method for interpretation of the mechanical behavior of piles in collapsible loess. There was good agreement between our experimental results and those from the literature and the results predicted using the proposed model, suggesting that the model can be used as a tool in the rational design of pile foundations in collapsible soils. [ABSTRACT FROM AUTHOR]

Geosynthetic encased stone columns are often designed using the conventional framework of saturated soils ignoring the influence of in-situ unsaturated soil conditions. This article evaluates the performance of stone columns with and without geosynthetic encasement extending the mechanics ofunsaturated soils. The focus of numerical simulations was directed towards understanding the influence of matric suction on the confining support offered by the surrounding soil to stone columns with and without geosynthetic encasement. Investigations were extended considering the stiffness and the length of the geosynthetic encasement. The numerical studies suggest the load-carrying capacity of stone columnincreased with an increase in the matric suction in the boundary effect and the primary transition zone. However, the contribution of matric suction towards load-carrying capacity starts reducing from the secondary transition zone. The information on boundary effect and transition zones can be derived fromthe soil-water characteristic curve, which is a relationship between the water content and soil suction. In addition, the effect of stiffness and length of encasing material in unsaturated soils was found to be in contrast with saturated soils. The results of the study are promising towards developing procedures thatcan be used in the rational design of stone columns in unsaturated soils.

Land subsidence associated with using natural groundwater resources for serving the growing population needs has been receiving extensive research attention in the literature over the past few decades. The water content fluctuation in the of subsurface soil layers significantly impacts the land subsidence. The key objective of this study is to predict changes in water content profiles in soil layers over a long period of time using a deep learning-based approach. A convolution neural network algorithm that is commonly used in Artificial Intelligence (AI) applications is modified in the present study for processing in-situ measurement water content profiles. The approach used in the proposed AI method has a distinct advantage for generating dynamic predictions based on the extracted spatiotemporal characteristics of the data. In addition, three different algorithms are compared with respect to time series prediction, including long-short-term memory (LSTM), multiple-layer perceptron (MLP) networks and autoregressive integrated moving average (ARIMA).

In this paper, numerical study results that highlight the capability of using pond ash as a cover material in covers with capillary barrier effects are succinctly summarized. A model was exclusively developed and calibrated using commercial software SEEP/W for this study. After calibration, the efficiency of pond ash as a coarse-grained layer (CGL), fine-grained layer (FGL), unsaturated drainage layer (UDL), and seepage control layer (SCL) was investigated using various combinations. The CCBE made of pond ash obtained from the output and input points of an ash pond as alternate fine- and coarse-grained layers were observed to perform well. The performance of pond ash as UDL and SCL was also observed to be good. The approach presented in this study is valuable in assessing likely slope failures of coal ash storage facilities that may be triggered by rainfall events. The study aids in significantly reducing rainfall infiltration, improving the overall stability of the slopes, and promoting sustainability by utilising the concept of “waste covering waste”. The approaches used in this study can be extended in the rational design of slopes to address the future challenges anticipated with unprecedent rainfall events and its negative impacts associated with climate change effects.

In this paper, water flow in a 4 m height column with an unsaturated soil that is subjected to multiple infiltration events for a 62 day period is investigated. One-dimensional (1D) numerical analysis is also undertaken to analyze the flow, extending the seepage theory for unsaturated soils. Results highlight the formation of two wetting fronts; namely, wetting front I and wetting front II that are induced by the first and subsequent infiltration events, respectively. There is a stable zone where the water content is approximately constant; it forms between the two fronts. A conceptual model of the suction profile is proposed for interpreting in situ water flow by dividing the unsaturated zone into four distinct zones; namely, active, steady, transition, and capillary fringe zones. This division is helpful for providing a rational explanation of water flow in different zones. Novel contributions from this study include a relationship between the hydraulic properties in the steady zone and the flow velocity, which is determined by an average influx rate. In addition, the rate of groundwater recharge can also be estimated using the average influx rate. Results of the present study are useful to understand and interpret the relationship between water infiltration and suction or water content profile in the unsaturated zone as well as variation of groundwater table level. Key words: water flow, unsaturated soil, column test, multiple infiltration events, suction profile. Dans cet article, l'ecoulement de l'eau dans une colonne de 4 m de hauteur avec un sol insature qui est soumis a de multiples infiltrations pendant une periode de 62 jours est etudie. L'analyse numerique unidimensionnelle (1D) est egalement entreprise pour analyser l'ecoulement et etendre la theorie de l'infiltration pour les sols insatures. Les resultats mettent en evidence la formation de deux fronts de mouillage, a savoir le front de mouillage I et le front de mouillage II, induits respectivement par la premiere infiltration et les infiltrations ulterieures. Il y a une zone stable ou la teneur en eau est a peu pres constante qui se forme entre les deux fronts. Un modele conceptuel de profil de succion est propose pour interpreter le debit d'eau in situ en divisant la zone insaturee en quatre zones distinctes, soit les zones active, stable, de transition et de frange capillaire. Cette division est utile pour fournir une explication rationnelle du debit d'eau dans differentes zones. Les nouvelles contributions de cette etude comprennent une relation entre les proprietes hydrauliques dans la zone stable et la vitesse d'ecoulement, qui est determinee par un debit d'entree moyen. De plus, le taux de recharge d'eau souterraine peut egalement etre estime a l'aide du taux d'afflux moyen. Les resultats de la presente etude sont utiles pour comprendre et interpreter la relation entre l'infiltration d'eau et le profil de succion ou de teneur en eau dans la zone insaturee ainsi que la variation du niveau de la nappe phreatique. [Traduit par la Redaction] Mots-cles: debit d'eau, sol insature, essai de colonne, evenements d'infiltration multiple, profil de succion., 1. Introduction Hydrologists, soil scientists, geotechnical and geoenvironmental engineers are significantly interested in the water flow behavior in unsaturated soils (Levine and Salvucci 1999; Rahimi et al. 2010). These studies [...]