有限元强度折减法中的刚度退化及边坡失稳判据

介绍了刚度退化的基本原理和方法及其在有限元计算中的实现,通过实例计算得出考虑刚度退化所得的安全系数比不考虑刚度退化所得的安全系数要小,这是因为:在有限元计算中随着强度参数的折减,坡体内部的某些点首先进入塑性状态,由于周围土体的约束作用,塑性区有发展的趋势,当泊松比ν增大、弹性模量E减小时,土体间的相互作用减弱,塑性区发展减缓,范围减小。所以塑性破坏点连成的区域比不考虑刚度退化时小得多,并且集中在潜在滑移面附近,构成剪切滑移带,致使有限元计算不收敛,边坡失稳破坏。利用刚度退化的有限元计算结果,通过对比分析强度折减和考虑刚度退化的强度折减的数值计算结果,认为塑性区是否贯通的判别标准不能确切反映边坡稳定状态。

Stiffness reduction and slope failure criterion in strength reduction finite element method

The basic theory and method of stiffness reduction and the implementation in FEM were introduced.The safety factor considering the stiffness reduction was smaller than that without regard to it because of that some points in slopes came into plastic state with the increase of strength reduction in finite element calculation,the plastic zone tended to expand under the constraint of the surrounding soil,but the expansion of the plastic zone became slow for the attenuated interaction among soil while the parameters ν and E were decreasing at the same time.The zone connected by Mohr-Coulomb and tension cut-off points was smaller than that without regard to the stiffness reduction,and these points concentrated nearby the potential sliding plane,and formed the shearing sliding band,so the calculated results by the FEM were not convergent,and the overall collapse occurred.Making use of the calculated results by the FEM,it was considered that the plastic zone developed from the slope toe to the top did not mean the overall collapse through comparison of the calculated results by the strength reduction FEM with and without of considering the stiffness reduction.