基于Hansbo渗流的理想砂井地基径向弹黏塑性固结分析

ANALYSIS OF RADIAL ELASTIC VISCO-PLASTIC CONSOLIDATION FOR IDEAL SAND-DRAINED GROUND BASED ON HANSBO’S FLOW

传统砂井固结理论没有考虑软黏土显著的流变特性以及渗流的非Darcy特性,常常导致计算结果与实际偏差较大。为进一步探究软黏土地区的砂井固结机理,通过引入考虑时间效应的统一硬化(UH)本构模型以及Hansbo渗流模型分别描述土体变形的非线性和渗流的非Darcy特性,在不考虑井阻和涂抹效应的情况下,对Barron自由应变假定下的砂井固结方程进行改进,并给出方程的隐式有限差分求解格式。与Berry的显式数值解的对比表明该算法是有效性的。据此对土体黏滞性以及Hansbo渗流参数对砂井非线性固结过程的影响进行分析。结果表明:软黏土的黏滞性使固结初期砂井影响区外边界附近的孔压升高,且黏滞性越强,这种现象就越明显;同时Hansbo渗流对孔压升高具有增强作用。但在固结的中后期,土体的黏滞性及渗流的非Darcy特性会延缓砂井地基中孔压的整体消散。

The traditional sand drain consolidation theory does not consider the significant rheological properties of soft clay and the non-Darcy characteristics of flow,which often leads to a large deviation between the calculated results and the observations. In order to further investigate the consolidation mechanism of sand drain ground in soft clay area,the nonlinear deformation of soil and the non-Darcy characteristics of flow were described by introducing uniform hardening (UH) constitutive model considering time effect and Hansbo’s flow model,respectively. The consolidation equation of sand drain ground under the Barron ’s free strain assumption was modified without consideration of the well resistance and smear effect,and its numerical solutions were obtained by using the implicit finite difference method. The validity of the proposed method was verified by comparison with Berry ’s explicit numerical solutions. Based on that,the influence of soil viscosity and Hansbo’s flow parameters on the nonlinear consolidation process of sand drain ground was analyzed. The numerical results showed that the viscosity of soft clay caused an increase in the pore pressure near the boundary of the influence zone of the sand filled drainage well at the early stage of consolidation,and the phenomenon became more obvious with the increase of viscosity. Meanwhile,Hansbo’s flow enhanced the phenomenon of increased pore water pressure. However,at the middle and late stages of consolidation,the viscosity of the soil and the non-Darcy behaviour of the flow would delay the overall dissipation of pore water pressure in the ground with sand drains.