现浇X形桩桩承式加筋路堤三维有限元分析

桩承式加筋路堤在高速公路软基处理中得到了广泛应用，但目前对其承载变形机制还缺乏深刻认识。结合南京长江第四大桥北接线段软基加固工程，基于数值方法对现浇X形桩桩承式加筋路堤中桩土沉降、桩土应力、桩身轴力及超静孔隙水压力的发展变化规律进行了分析。研究结果表明，受土拱效应影响，路堤填筑荷载主要由桩体承担，桩及桩间土土压力在路堤填筑过程中均逐渐增大，在软基固结过程中，桩顶土压力继续增大而桩间土土压力逐渐减小，最终趋于各自的稳定值；路堤填筑过程中桩身轴力增长较快，现浇X形桩桩身上部较大部分区段存在负摩阻力，桩身中性点位置经历了先逐渐上移、而后向下移动，最终趋于稳定的过程。

Three-dimensional finite element analysis of geogrid-reinforced embankment supported by X-section cast-in-place piles

Geogrid-reinforced and pile-supported expressway embankment has been widely applied to soft ground improvement; but its bearing and deformation mechanism has not been deeply understood. Combining with the Fourth Yangtze River Bridge’s north-line soft ground reinforced project in Nanjing, the numerical method is used to analyze the variations of settlement and stress of pile and soil, pile axial force and excess pore water stress. The results show that road embankment load is mainly borne by piles as a result of the soil arching effect. The soil pressures of pile and soil increase with the development of embankment load firstly; and then the pressure of pile continue to increase while the pressure of soil decreases in the consolidation process of soft soil. The pile axial force increases quickly during the process of filling. Negative skin friction develops along most part of X-section cast-in-place pile shaft; and the neutral point ascends firstly; with the consolidation of soil, the depth of the neutral point becomes deeper; then the neutral point position is unaltered at the end of soil consolidation.