考虑Hansbo渗流的饱和黏土一维弹黏塑性固结分析

One-dimensional elastic visco-plastic consolidation analysis of saturated clay considering Hansbo’s flow

为进一步深入探讨饱和黏土的固结机制,引入考虑时间效应的统一硬化(UH)本构模型描述饱和黏土变形的弹黏塑性,以及Hansbo渗流方程描述固结过程中的非Darcy渗流,修正了饱和黏土一维固结方程,并利用有限差分法进行了求解。通过与文献中一维流变固结试验结果和理论计算结果的对比,验证了所提计算方法和UH模型的适用性。然后探讨了Hansbo渗流参数及UH模型参数对流变固结过程的影响。计算结果表明:土体的黏滞效应是引起流变固结初期地基不排水面附近出现孔压升高现象的主要原因,而渗流的非Darcy特性增强了这一效应,同时土体的这两个特性还延缓了固结中后期饱和黏土地基中孔压的整体消散和地基的沉降。另外,随着回弹指数和超固结参数的增大,或渗透指数的减小,上述流变固结特性更加明显。但是Hansbo渗流参数和渗透指数对地基最终沉降量均无影响。

To further investigate the consolidation mechanism of saturated clay,the unified-hardening(UH)constitutive model considering the time effect was introduced to describe the elastic visco-plasticity of saturated clay soil as well as the Hansbo’s equation to describe the non-Darcy flow in the consolidation process.Accordingly,Terzaghi’s one-dimensional consolidation equation of saturated clay was modified,and the numerical analysis was conducted by using the finite difference method.In order to verify the applicability of the present method and the UH model,the numerical solutions provided by the present method for the cases that the flow of pore water obeys Darcy’s law were compared with the theoretical and experimental results based on one-dimensional rheological consolidation theory in the literature.Then the effects of Hansbo’s flow parameters and the UH model parameters on the rheological consolidation process were investigated.The calculation results show that the viscous effect of soil leads to an increase of pore water pressure near the impervious boundary at the early stage of consolidation,and the behaviour of the non-Darcy flow enhances this phenomenon.These two characteristics of soil also control the overall dissipation rate of excess pore water in the saturated clay layer,thereby reduce the settlement rates of the soil layer during the middle and late stage of consolidation.In addition,these aforementioned consolidation behaviours become more obvious with the increase of swelling index and overconsolidation parameter of soil.But the parameters of Hansbo’s flow and the permeability index have no effect on the ultimate settlement of the soil layer.