Numerical study of impact of soil anisotropy on seismic performance of retaining structure

Recent laboratory investigations indicate that the stress-strain-strength responses of loose granular soils are appreciably affected by the fabric orientation of the soil relative to the frame of principal stresses. A sand specimen exhibiting a dilative response during triaxial compression may show a contractive response during triaxial extension under otherwise identical conditions. This observation is of practical importance for applications concerning with essentially undrained loading conditions because the effective mean normal stress at failure. Consequently, the shear strength associated with an undrained contractive path is considerably lower than those following a dilative path. This raises a question about the impact of soil anisotropy on seismic performance of retaining structures subjected to active and passive earth pressures, because the directions of principal stresses in retained soils for the two cases are very different. This paper presents a set of fully coupled finite element analyses incorporating an anisotropic sand model. The analyses reveal that the impact of fabric anisotropy could be significant when the retaining structure is under passive earth pressure conditions.It shows that the impact of fabric anisotropy on soil dilatancy, and consequently the critical state strength, should be taken into consideration in performance-based design of passive earth pressure loaded retaining structures.