砂土地基上条形浅基础破坏包络面

Failure Envelope of Strip Shallow Footings on Sand

对于砂土地基上条形浅基础在倾斜与偏心荷载作用下承载力进行了比较系统的平面应变有限元分析.在分析中,砂土假定为纯摩擦材料,遵循基于Mohr-Coulomb破坏准则的理想弹塑性本构关系.首先对条形浅基础的竖向承载力进行了有限元计算,并与滑移线解法进行了对比,两种方法所得结果比较吻合.进而探讨了砂土内摩擦角对于基础在竖向荷载V与水平荷载H、竖向荷载V与弯矩M荷载平面内的破坏包络轨迹的影响,揭示了地基在不同荷载分量组合条件下的失稳破坏机制.计算结果表明,与不排水情况下软黏土地基上基础破坏包络面相比,砂土地基上条形浅基础的破坏包络面形状有较大差异,但V-H和V-M平面内的破坏包络面形状仍具有较好的归一化特性.基于有限元计算结果,分别建议了条形浅基础在倾斜与偏心荷载作用下的破坏包络面方程,该方程可用来合理评价复杂荷载条件下砂土地基上条形浅基础稳定性.

The bearing capacity of strip shallow footings subjected to inclined load and eccentric load on sand was explored through plane strain finite element numerical analyses. The sand is assumed to be purely frictional and obeys elasto-perfectly plastic relationship following the Mohr-Coulomb failure criterion. The capacity of strip shallow footing under centrally vertical load was computed,and the calculated results agreed well with those derived from slip-line field theory. Then the influence of soil friction angle on the V-H and V-M failure locus was investigated. The soil deformation mechanism under various combinations of load components was illustrated. The results show that the shape of failure envelopes of shallow footings on sand is notably different from that on undrained clay,but normalization of the failure envelope on the V-H and V-M load plane by the pure vertical bearing capacity allowed it to be generalized for varying conditions. Based on finite element analyses,the equation of failure envelope on the V-H and V-M plane is proposed respectively,which can be used to evaluate the stability of strip shallow footings on sand under complex loading condition.