路堤荷载下含硬壳层软土地基破坏模式

摘要

通过理论分析和数值计算,对比分析在路堤荷载作用下含有连续和不连续硬壳层的水平层状软基的破坏模式,针对路堤坡脚外硬壳层不连续的情况(如存在鱼塘等),提出以局部剪切破坏模式失稳的破坏模式判定参数,即临界距离Lcr;借助正交试验原理,对Lcr的影响因素进行分析,给出各因素的敏感性顺序;利用逐步回归迭代方法,分别给出上限临界距离LcrU和下限临界距离LcrD的数学表达公式,并根据工程实例的验算论证了其可靠性.结果表明:在路堤荷载作用下,硬壳层连续时软基为整体剪切破坏;硬壳层不连续时,当不连续断面与坡脚的距离小于LcrU或大于LcrD时软基为整体剪切破坏,当不连续断面与坡脚的距离大于LcrU且小于LcrD时软基为局部剪切破坏.硬壳层厚度为Lcr的主要影响因素,软土层厚度为次要因素,硬壳层内摩擦角和黏聚力对其影响较小.%Aiming at the discontinuity of hard crust outside the toe of embankment ( such as fishpond, etc. ) , through theoretical analysis and numerical simulation, the failure mode of a soft soil layered foundation with continuous and discontinuous hard crust has been compared and analyzed under the embankment load, and a judgment parameter of failure mode, namely the critical distance Lcr, is proposed to distinguish between the general shear failure mode and the local shear failure mode. With the principle of orthogonal test, factors that influence Lcr have been analyzed, and each factor is given in order of sensitivity. Then, using the iterative method with stepwise regression, mathematical formulas of upper ( LcrU) and lower ( LcrD) limits of the critical distance are given respectively, and their reliability are demonstrated by checking an engineering project. The results indicate that the failure mode of soft soil foundation with continuous hard crust is general shear failure. When the hard crust layer is discontinuous, the failure mode is general shear failure if the distance between discontinuous section and embankment toe is less than LcrUor higher than LcrD, and local shear failure if the distance is between LcrUand LcrD. The thickness of hard crust layer is the main factor to Lcrand the secondary factor is the thickness of soft soil layer, while the influence caused by the internal friction angle and the cohesion of hard crust layer is smaller.