边坡稳定有限元分析中的三个问题

对大型有限元软件ABAQUS进行二次开发,提出了自动搜索安全系数的边坡稳定有限元分析模型。在此基础上进行大量变动参数研究,探讨了迭代不收敛、塑性区贯通及等效塑性应变贯通等3种边坡失稳判据的内在联系与适用性,其中迭代不收敛判据易于自动搜索的编程实现,且较少依赖研究者的经验。大多数情况下单元阶次不影响安全系数的确定,但一阶单元有时可能高估安全系数,建议采用二阶单元。基于更新拉格朗日格式实施边坡稳定大变形有限元分析,结果表明迭代不收敛准则不适用于大变形分析。

Three problems in slope stability analyses with finite element method

To study the slope stability with shear strength reduction technique, a large finite element (FE) software, ABAQUS, is customized and linked into our program with the function of automatic searching for the safety factor. Based on results from FE model developed, three indicators of slope failure, e. g. non-convergence of solution, the plastic zone extending from the slope toe to the top and the critical value of plastic strain along the potential failure surface, are discussed. Furthermore, the inherent association of three failure indicators is illustrated. The non-convergence criterion is fit for coding the program with automatic searching for safety factor, as well as less dependant on users’ experiences. In most cases the order of mesh elements slightly affects the safety factor, but linear elements tend to overestimate the safety factor sometimes. It is thus advised to adopt second-order elements. Large deformation FE analyses for slope stability were carried out in updated Lagrangian formulation; and it is found the non-convergence criterion can not be taken as a reasonable indicator of slope failure.