变荷载下考虑半透水边界和起始水力坡降的软土一维固结解析解  

Analytical solution for one-dimensional consolidation of soft soils under a partially permeable boundary condition and a time-dependent loading considering the threshold hydraulic gradient

作　　者：陈余 李传勋[1] 冯翠霞 CHEN Yu;LI Chuan-xun;FENG Cui-xia(Faculty of Civil Engineering and Mechanics,Jiangsu University,Zhenjiang,Jiangsu 212013,China;Shanghai Shenyuan Geotechnical Engineering Co.,LTD,Shanghai 200011,China)

机构地区：[1]江苏大学土木工程与力学学院,江苏镇江212013 [2]上海申元岩土工程有限公司,上海200011

出　　处：《岩土力学》2021年第11期3008-3016,3040,共10页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.51878320)。

摘　　要：在软土地基顶面铺设的不可压缩垫层对边界排水性能具有一定影响,同时软黏土中渗流偏离Darcy定律的现象对超静孔隙水压力消散的影响已逐渐被人们所熟知。但同时考虑不可压缩垫层与地基土体接触面处形成的半透水边界和起始水力坡降的固结理论却少有报道。建立了变荷载下同时考虑半透水边界和起始水力坡降的一维固结模型,采用特征值法、Laplace变换对所建立的固结模型开展解析求解,分析了固结模型在不同边界条件、起始水力坡降以及加载速率下的固结特性。结果表明:考虑起始水力坡降后,半透水界面参数φ(不可压缩层渗透系数和黏土层厚度之积与黏土层渗透系数和不可压缩层厚度之积的比值,其值大小代表排水面透水能力强弱)值越小,孔压消散速率越慢,固结完成所需时间越长;φ值越大,孔压消散速率越快,固结完成时间越短。半透水边界条件下起始水力坡降的无量纲变量R(起始水力坡降、水的重度与土层厚度三者之积除以外荷载)值越大,渗流前锋(移动边界)到达土层底部的时间越长,固结完成时土中超静孔压残留值越大。相同时刻下,按变形定义的土层平均固结度随R值增大而增大,但按孔压定义的土层平均固结度随R值增大而变小。加载速率对考虑起始水力坡降和半透水边界的土层固结性状具有明显影响,加载速率越慢,超静孔隙水压力峰值越小,且达到峰值所需时间越长,但加载速率对最终超静孔压残留值几乎无影响。The placement of an incompressible cushion on the top of soft soil deposits affects the boundary drainage conditions. It has been well documented in the literature that the seepage through soft clays deviates from Darcy’s law, which affects the dissipation of excess pore water pressure. However, the studies on the soil consolidation behavior under the partially permeable boundary condition induced by the incompressible cushion underlain by soil deposits considering the non-Darcian flow with the threshold hydraulic gradient have rarely been reported. In this study, a one-dimensional consolidation model under the partially permeable boundary condition and the time-dependent loading is developed. The effect of the threshold hydraulic gradient on the water flow through the soft soil is taken into account. The analytical solution is derived for the proposed consolidation model based on the eigen value method and Laplace transform. Based on the derived analytical solution, the sensitivity analysis has been conducted for the consolidation behavior under various boundary conditions, threshold hydraulic gradients and loading rates. It indicates that the smaller the partially permeable boundary parameter φ(i.e., the ratio of the product of the coefficient of permeability of the incompressible cushion and the thickness of the clay deposit to the product of the coefficient of permeability of the clay deposit and the thickness of the incompressible cushion, which indicates the permeability of the partially permeable boundary)is, the slower the dissipation of excess pore water pressure and the longer the duration of consolidation process are;the larger j is, the faster the dissipation of excess pore pressure and the shorter the duration of consolidation process are. The larger the dimensionless variable R(the ratio of the product of the threshold hydraulic gradient, the unit weight of water and the thickness of soil layer to the surcharge) is,the longer the time when the seepage front(i.e., moving boundary) reaches the bott

关 键 词：变荷载 一维固结 半透水边界 起始水力坡降 解析解 

分 类 号：TU470[建筑科学—结构工程]