路堤荷载下DJM-PVD复合地基固结特性数值分析

以淮盐高速公路现场试验段为原型,采用数值分析方法分析了路堤荷载下DJM-PVD复合地基的固结机理和桩土应力分配特性.数值计算中采用单元体模型来代表复合地基.数值分析结果表明:路堤荷载下,DJM-PVD复合地基上部中桩间土沉降大于桩体沉降,桩端附近桩体沉降大于桩间土沉降,存在桩土差异沉降,桩土差异沉降使得桩间土承担荷载和桩体承担荷载相互转移;复合地基的桩体应力集中、桩体应力比等与均桩土差异沉降的发展密切相关;DJM-PVD复合地基的固结机理主要包括3部分:排水板的排水效应、粉喷桩的应力集中效应以及桩土间荷载转移形成的孔压梯度,三者均能加速地基的固结,减少工后沉降.

Numerical analysis for performance of ground improved by DJM-PVD combined method

Based on the field tests,the numerical method was employed to analysis the performance of ground improved by DJM-PVD(dry jet mixing-prefabricated vertical drains) combined method under embankment.The solutions were obtained by using the unit cell model,which consists of the column and the tributary surrounding soil within a column zone of influence.The results indicate that: the local differential settlement develops between the column and its surrounding clay under embankment,which may induce the transfer of stress between surrounding soil and column;the local differential settlement between surrounding soil and column effect the stress on the column and the stress concentration ratio;and the consolidation of ground improved by DJM-PVD combined method is accelerated by the drainage of PVDs, the stress concentration on column and the excess pore water pressure gradient resulting from the stress transfer between surrounding soil and column.