考虑基质吸力影响的非饱和路堤三维稳定性上限分析

A three-dimensional upper-bound limit analysis of unsaturated embankment considering matric suction

采用极限上限分析定理构建了路堤失稳的三维旋转破坏机构,继而根据Bishop非饱和土抗剪强度理论,考虑非饱路堤内部基质吸力的空间分布及其随地下水位的变化,建立了路堤破坏土体外力功率与内部能量耗散功率的能量守恒方程,并利用遗传算法编写了非饱和路堤最小上限解的高效搜索算法。通过将非饱和土路堤基底破坏模式退化为边坡破坏模式,并与现有非饱和土边坡稳定性计算结果对比,验证了所提上限解的正确性和遗传搜寻算法的准确性。进一步地,对路堤三维稳定性的关键影响因素展开了系统分析,研究了路堤填土孔径分布、基质吸力、进气值倒数、路堤倾角以及有效内摩擦角等因素对路堤三维稳定性的影响规律。研究表明,非饱和土质路堤的稳定性不仅取决于路堤填土性质,而且依赖于影响土体吸力大小与分布的填土孔径参数和进气值等因素。地下水位升降引起的基质吸力变化对路堤稳定性存在显著影响。研究结果为路堤稳定性精细化分析提供了重要的理论依据。

A three-dimensional rotational failure mechanism of embankment was built based on the upper limit analysis theorem.Drawing on the shear strength theory of Bishop unsaturated soil and considering the spatial distribution of matrix suction inside the unsaturated embankment and its change with the groundwater level,the energy conservation equation encompassing the external force work rate and the internal energy dissipation rate of the embankment was established.An efficient genetic algorithm was developed to search for the least upper-bound value of unsaturated soil embankment.By degrading the unsaturated soil embankment failure mode into a slope failure mode and comparing critical values with existing unsaturated soil slope stability calculations,the correctness of the proposed upper-bound values and the accuracy of the genetic search algorithm were verified.Furthermore,the influence of the pore size distribution,matrix suction,the inverse of the air entry value,embankment inclination angle and effective internal friction angle on the three-dimensional stability of the embankment was systematically studied.The results demonstrated that the stability of unsaturated soil embankment depends not only on the properties of soil but also on the pore size parameters and the inverse of the air entry value.Additionally,the fluctuation of matric suction resulting from changes in groundwater levels significantly impacts the stability of unsaturated soil embankments.These findings offer an important theoretical basis for granular analysis of embankment stability and the design of ultimate fill height,providing valuable insights for improving embankment stability analysis and facilitating the design of embankments.