软土地基堆载预压处理失效及二次处理分析

Analysis on failure of surcharge preloading and secondary treatment of soft road subgrade

结合某市政道路软土地基处理工程实例,分析原堆载预压地基处理方案中地表沉降发展缓慢、沉降量偏小的原因,进而提出补打砂井的二次地基处理措施。结合Plaxis有限元分析软件,采用平面应变等效分析方法,对补打砂井的间距和深度设计参数进行了二维数值模拟,对比了不同砂井间距和深度组合下的沉降发展和超孔隙水压力消散情况。研究结果表明:补打砂井能明显加快软土地基固结沉降;砂井深度和间距变化对沉降的发展和孔压消散均有明显的影响;相比于减小砂井间距,增大砂井深度对下层淤泥质粉质黏土层的孔压消散效果更好;同时给出了本工程砂井深度和间距的建议值,可为今后类似工程提供一定参考。

Based on a ground treatment practice of a soft road subgrade, the causes accounting for the small and yet slow settlement development were analyzed. Consequently, a secondary ground treatment method, i.e., installing vertical drains, was proposed. The design parameters including the spacing and depth of the vertical drains were modeled with the two-dimensional finite element software, Plaxis. The two-dimensional modelling was justified for a three-dimensional practical situation since an equivalent plain strain analysis was taken. The effects of the spacing and depth of the vertical drains on the ground settlement and the excess pore pressure dissipation were analyzed. The results show that the consolidation settlement and excess pore pressure dissipation of ground can be accelerated after installing the vertical drains. Compared with shortening the spacing of sand wells, increasing the depth of sand wells has a better effect on the pore pressure dissipation of the lower mucky silty clay layer. The values of the spacing and length of the drains are suggested for the present study, which would provide reference for similar projects.