变荷载下劲性搅拌桩复合地基固结分析

采用劲性搅拌桩加固地基的复合地基技术越来越多地被用于实际工程，而对其固结理论的研究有待深入。基于等应变假定，推导出劲性搅拌桩复合地基在变荷载作用下桩间土的固结方程，采用双层地基一维固结理论求解该固结方程，得到了桩间土中的平均超静孔隙水压力和复合地基整体平均固结度的解析表达式。通过与固结度有限元分析结果的比较，评价了固结度解析表达式的计算精度。利用该固结度解析表达式进行参数分析，研究了劲性搅拌桩复合地基的固结特性。研究结果表明，劲性搅拌桩复合地基的固结速率远大于传统的水泥搅拌桩复合地基，它随着劲性搅拌桩的置换率、芯桩芯长比和水泥土外壳材料压缩模量的增大而增大。芯桩的截面含芯率和压缩模量对复合地基固结速率影响很小。

Consolidation analysis of composite ground with stiffened deep cement mixing piles under time-dependent loading

The composite ground with stiffened deep cement mixing (SDCM) piles has been widely used. Nevertheless, there are limited researches on its consolidation theory. Based on the equal strain assumption, the equations governing consolidation of the surrounding soil within the composite ground with SDCM piles were derived under time-dependent loading. On the basis of one dimensional consolidation theory of a double-layer ground, the analytical solutions were then developed for the consolidation of the composite ground，including the average excess pore water pressures in the surrounding soils and the overall average degree of consolidation of the composite ground. In order to verify the correctness and accuracy of the proposed analytical solutions, comparison of the consolidation rates by the proposed analytical solution and the FEM was made. Parametric study was conducted to investigate the consolidation behavior of this new type of composite ground using the proposed analytical solution. The results show that the consolidation rate of the composite ground with SDCM piles is much greater than that of the conventional composite ground with deep cement mixing (DCM) piles. It increases with the increasing of the core-pile length ratio, the area replacement ratio and the constrained modulus of DCM pile socket. The constrained modulus of the core pile and its area core ratio have insignificant influence on the consolidation rate of the SDCM pile reinforced ground.