非线性破坏准则对被动土压力的影响

在上限定理的基础上,根据非线性破坏准则,对墙后填土建立机动容许的速度场,运用流动法则以及速度边界条件求解被动土压力的上限解。首先通过“切线法”引进变量,然后对墙后填土建立三种含有变量的速度场,求出被动土压力的目标函数与约束条件,最后根据“序列二次规划算法”对该问题进行优化。数值结果表明:当非线性破坏准则变为线性破坏准则时,结果与前人的成果一致;非线性参数对被动土压力有重要影响。

INFLUENCES OF A NONLINEAR FAILURE CRITERION ON PASSIVE EARTH PRESSURE

The passive earth pressure problem is studied by means of the kinematical approach of limit analysis theory. The filling soil behind rigid retaining wall is perfectly plastic, whose failure is governed by a nonlinear Mohr-Coulomb failure criterion. Three kinds of knematically admissible failure mechanisms are considered for the calculation schemes. The main differences among the three failure mechanisms are velocity vectors between soil and wall. The objective functions are obtained by equating the work rate of external force to internal dissipation along the velocity discontinuities. The upper bound solutions are presented by applying a nonlinear sequential quadratic programming (SQP) algorithm. From the numerical results, it can be seen that the nonlinear failure parameter has a significant effect on the passive earth pressure and the three translational failure mechanisms are equivalent for computing passive earth pressures. If the nonlinear Mohr-Coulomb yield criterion turns into a linear Mohr-Coulomb yield criterion, then the solutions presented in this paper agree well with available predictions.