变荷载下双层不排水桩复合地基一维固结分析

Analysis of 1D Consolidation of Double-layered Composite Foundation with Impervious Pile under Time-dependent Loading

假定弱排水桩复合地基中的桩体不排水,同时考虑地基土的成层性与荷载随时间任意变化两个条件,导出了变荷载下双层不排水桩复合地基的一维固结控制方程,得到了此类地基中超静孔隙水压力的一般解析解,并给出了瞬时加载和单级等速加载两种常见情况下超静孔隙水压力和固结度的解答;然后,通过将本文解退化为经典解和与算例分析两种途径验证了本文解析解的合理性;最后,利用编程计算分析了双层不排水桩复合地基的固结规律。结果表明:随着桩径比的减小、桩体刚度的增大和加荷速率的增大,固结速率会增大;k_(v2)/k_(v1)越大,E_2/E_1越大,h_2/h_1越小,则固结越快;分别按平均孔压和按沉降定义的双层不排水桩复合地基固结度会有差别,差别大小与各层土体的压缩模量有关。

Assuming that the weak drainage piles are undrained in composite foundation, considering both layered soils and time-dependent loading, we derived the 1D consolidation control equations of double-layered composite foundation with impervious pile under time-dependent loading, and obtained the general analytical solutions of the excess pore water pressure of such foundation. Then, we gave the analytical solutions of the excess pore water pressure and the consolidation degree in the common cases of instantaneous loading and single-stage constant loading respectively. After that, we verified the reasonableness of the analytical solution through the ways of numerical example and the degradation of the solutions in this article to classical solutions. Finally, we investigated the consolidation rule of double-layered composite foundation with impervious pile by programming computation. The result shows that （ 1 ） the consolidation rate will increase when the pile stiffness increases and loading rate increases while the pile diameter ratio decreases;（2） when kv2/kv1 is greater, h2/h1 is smaller and E2/E1 is greater, the consolidation rate is greater; （ 3 ） the consolidation degrees are different when defined by average excess pore water pressure and settlement respectively, and the size of difference is related to the soil＇s compression modulus of each layer.