刚性基础下组合渗流碎石桩–不排水桩复合地基固结分析

Consolidation analysis of stone column-impervious pile composite ground underneath rigid foundation considering radial and vertical flows within stone columns

基于等竖向应变假设,考虑桩碎石桩的径、竖向井阻和不同桩体周围的涂抹效应,推导出瞬时加载条件下碎石桩–不排水桩复合地基的固结控制方程,在单面排水条件下建立相应的固结解析解,包括复合地基整体平均固结度解答。将解析解计算出的复合地基固结速率与有限元数值解进行比较,验证解析解的合理性。利用建立的固结解析解进行参数分析,获得组合渗流碎石桩–不排水桩复合地基的固结特性。结果表明:在桩体置换率相等的条件下,碎石桩–不排水桩复合地基的固结速率远大于不排水桩复合地基,略小于碎石桩复合地基。碎石桩–不排水桩复合地基的固结速率随碎石桩和不排水桩置换率和压缩模量的增加而增大。碎石桩直径较大时复合地基固结速率随碎石桩径、竖向井阻的增加而减小,碎石桩直径较小时径向井阻的影响可以忽略不计。不排水桩桩侧土的扰动对复合地基固结速率的影响很小,实际工程设计中可以忽略不计。

The equal vertical strains were assumed and the smear effect in subsoil surrounding the stone columns and impervious piles and the well resistances in the stone columns in vertical and radial directions were considered,so that the differential equations governing the consolidation of stone column-impervious pile composite ground were derived under the instant loading. The corresponding analytical solutions were developed under the PTIB condition,including the overall average degree of consolidation of this type of combined composite ground. The proposed solution was verified through the comparison with the results from finite element method. A parametric study was conducted using the proposed solution to investigate the consolidation behavior of the composite ground. The results show that the consolidation rate of the soft ground improved by the stone columns combined with impervious piles is much faster than that of the composite ground with impervious piles,but slightly slower than that of the composite ground improved by stone columns. The consolidation rate increases with increasing of the area replacement ratio and constrained modulus of the stone columns or the impervious piles,but decreases with the increasing of the two-dimensional well resistances in the stone columns when the diameter of the stone column is bigger. The effect of the radial well resistance on the consolidation rate is negligible when the diameter of the stone column is smaller. The disturbance of the subsoil surrounding impervious piles has negligible influence on the consolidation rate of the composite ground.