循环荷载下软黏土不排水强度弱化分析的动力有限元ABAQUS实现

在波浪循环荷载作用下饱和软黏土地基出现孔隙水压力升高，并导致不排水强度弱化，严重影响防波堤的承载性能。考虑静偏应力影响，基于最大孔隙水压力发展模型和正常固结软黏土不排水强度公式，推导出软黏土不排水强度随循环荷载作用次数和应力水平变化的动态折减规律。结合软黏土不排水强度动态折减规律和M-C屈服准则，在有限元软件ABAQUS上实现软黏土不排水强度循环弱化分析的数值开发和动力运算过程。运用该动力有限元方法对天津港防波堤地基软黏土的动、静三轴试验进行数值模拟运算。结果表明，最大孔隙水压力发展曲线以及循环荷载作用后不排水强度的数值预测结果与动三轴试验结果吻合良好。另外，动力有限元方法（DFEM）能够表示土体强度在循环荷载作用下的具体弱化过程。

Dynamic finite element analyses of undrained strength degradation of soft clay in ABAQUS under cyclic loading

Post-cyclic undrained strength degradation happens to the saturated soft clay under wave cyclic loading for the excess pore pressure produced, resulting in the significant loss of bearing capacity of the breakwater. Based on the development model of pore pressure and the rule of shear strength of normally consolidation soft clay, the dynamic degradation law of soft clay strength is derived considering the effect of initial static deviator stress. Based on the dynamic degradation law and Mohr-Coulomb yield strength, the numerical development and dynamic calculation process for post-cyclic undrained strength degradation is implemented into software ABAQUS. Numerical simulations of the dynamic and static triaxial tests of Tianjin soft clay are conducted using the proposed dynamic finite element method. Results show that the development curve of maximum excess pore pressure and values of post-cyclic undrained strength predicted by the finite element method are acceptable compared with tests. Moreover, the proposed method can predict the process of post-cyclic strength degradation.