考虑非Darcy渗流的砂井地基弹黏塑性固结分析

Elasto-viscoplastic consolidation analysis of ground with sand drains considering non-Darcian flow

摘要:

为进一步研究饱和软黏土的砂井固结机制,采用Hansbo渗流方程描述渗流速度与水力梯度之间的非线性关系,同时引入考虑时间效应的统一硬化(UH)本构模型描述土体的弹黏塑性变形,重新推导理想砂井地基固结方程,给出隐式有限差分法求解的离散格式,并编制相应的Fortran计算程序.通过与已有砂井地基非线性固结解析解的对比,证明了求解方法的有效性.随后,探讨UH模型参数及Hansbo渗流参数对砂井地基弹黏塑性固结的影响规律.结果表明:土体主、次固结耦合机制是引起固结初期超孔隙水压力升高的主要原因,而且土体的黏滞性和渗流的非达西特性延缓了固结中后期砂井地基中孔隙水压力的整体消散.另外,在流变固结后期,增大渗透指数将加快固结进程.

Abstract:

In order to further investigate the consolidation mechanism of saturated soft clay ground with sand drains, Hansbo’s flow equation was adopted to describe the nonlinear relation between flow velocity and hydraulic gradient, and the unified hardening (UH) constitutive model considering time effect was introduced to describe the elasto-viscoplastic deformation of soil. The consolidation equation of ideal sand-drained ground was modified, the discrete scheme of implicit finite difference method was given, and the corresponding Fortran program was designed. By comparing the numerical solution with the existing analytical solution of nonlinear consolidation of sand-drained ground, the effectiveness of the proposed method was verified. Then, the influences of the parameters of UH model and Hansbo’s flow on the elasto-viscoplastic consolidation process of ground with sand drains were discussed. Numerical results show that the coupling mechanism of primary and secondary consolidation was the main reason for the increase of excess pore water pressure at the early stage of consolidation. The viscosity of soil and the non-Darcy characteristics of flow both delayed the overall dissipation of pore water pressure in the sand-drained ground at the middle-late stage of consolidation. In addition, the consolidation process was accelerated with the increase of the permeability index at the later stage of consolidation.