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The combined effect of stress and seepage is an important reason of engineering geological problems such as landslides, dam failures, and tunnel collapse. However, due to the limitations of the test apparatus, the existing studies rarely consider the stress effect in the seepage process. In this study, a soil column apparatus based on the wetting front advancing method was developed to explore the permeability properties of intensely weathered sandstone in a wide range of suction (10~106 kPa). The results suggest that the wetting front advancing velocity decreased as the vertical stress increased during infiltration, which indicates that the stress changes the infiltration channel and affects the infiltration rate. On the other hand, due to the water sensitivity of intensely weathered sandstone, the soil column deformation before and after wetting is significantly different, indicating that water infiltration further exacerbates the deformation. When vertical stress is applied to the soil column, the permeability coefficient-suction curves at different sections are paralleled in general, which is affected by the variation in dry density and the non-uniform distribution of stresses inside the soil column. Moreover, as the initial dry density increases, the influence of the vertical stress on the permeability coefficient gradually decreases. Key words: unsaturated soils, stress, permeability, hydro-mechanical coupling, wetting front, Introduction In mountainous areas with complex geological conditions, tunnel construction inevitably passes through extremely soft rocks, which are composed of soil formed by the weathering and decomposition of clastic rocks, [...]

Pore water chemistry can exert significant controls over the chemo-mechanical behavior of chemically active soils, which has not been characterized by using the traditional Terzaghi's effective stress to a satisfactory extent. In this paper, based on the concept of intergranular stress, a generalized effective stress for saturated active soils is reconceptualized and incorporated into the framework of the modified Cam–Clay (MCC) model to describe the mechanical response of soils upon complex chemical and mechanical loadings. The proposed model is capable of capturing very well the diverse features of the chemo-behavior of saturated active soils, while inheriting all the advantages of the MCC model, by introducing only one additional parameter. Within this context, a simple equation is derived to predict the development of swelling pressure with the variation of pore water chemistry. It is shown that the proposed swelling-pressure equation predicts very well the development of swelling pressure for expansive soils with a dilute pore solution, though discrepancy appears at high concentration. Because the double layer of clay particles is severely suppressed at high salt concentration, the microfabric of soil can be significantly changed, pointing to the importance of taking into account the effect of soil fabric in the constitutive modeling of active soils with high pore water concentration. [ABSTRACT FROM AUTHOR]

This study proposes an approach to simulate the effects of initial density on the relative coefficient of permeability for unsaturated soils. The density-dependent permeability function is derived based on (i) an incremental relationship between the degree of saturation and the initial void ratio with various suctions and (ii) the relationship between the permeability function and the soil-water retention curve (SWRC). Only one additional parameter is required in the proposed function, which can be calibrated using a conventional SWRC test. A number of test results in the literature are employed to validate the proposed density-dependent permeability function, and the model predictions indicate good agreement with the experimental data in the literature. Key words: unsaturated soil, soil-water retention curve, permeability function, initial density. Cette etude propose une approche pour simuler les effets de la densite initiale sur le coefficient relatif de permeabilite pour les sols non satures. La fonction de permeabilite dependante de la densite est derivee a partir de (i) une relation incrementale entre le degre de saturation et l'indice des vides initial a diverses succions, et (ii) la relation entre la fonction de permeabilite et la courbe de retention d'eau (CRE). Un seul parametre additionnel est necessaire dans la fonction proposee, qui peut etre calibre avec un essai de CRE conventionnel. Plusieurs resultats d'essais provenant de la litterature ont ete utilises pour valider la fonction de permeabilite dependante de la densite proposee, et les predictions du modele indiquent une bonne correspondance avec les donnees experimentales de la litterature. [Traduit par la Redaction] Mots-cles: sol non sature, courbe de retention d'eau du sol, fonction de permeabilite, densite initiale., Introduction The coefficient of permeability (or hydraulic conductivity) is one of the inevitable parameters to determine the hydraulic property of soils. For a soil, the coefficient of permeability (k) is [...]

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