砂土各向异性对挡土墙抗震性能影响数值分析

指出相同砂土在不排水三轴拉伸条件下测得的临界状态强度远低于在三轴压缩条件下的强度,这归因于土的各向异性.挡土墙在地震作用下变形与破坏的程度与填土的临界状态强度密切相关.正确估计土的强度对于评价挡土墙的抗震性能具有重要意义.对于受被动土压力作用的挡土墙,如果不考虑土的各向异性,可能会过高估计土的临界状态强度,即土液化后能够提供的被动土压力的大小,从而过高估计挡土墙的安全储备.对挡土墙抗震性能进行完全耦合有效应力分析,计算结果表明:对于受被动土压力作用的挡土墙,砂土内在各向异性对其抗震性能影响显著;对于受主动土压力作用的挡土墙影响轻微.

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.