考虑起始水力坡降的天然非均质地基固结分析

实际工程中通常为未经处理的天然非均质地基。低水力坡降下黏性土中渗流存在起始水力坡降的现象也逐渐被认可，但能考虑起始水力坡降的非均质地基固结模型鲜见报道。基于具有起始水力坡降的渗流模型，考虑实际中的变荷载，对压缩模量和渗透系数随深度变化的非均质地基固结问题展开研究。通过压缩模量随深度增加及渗透系数随深度减小考虑天然地基的非均质性，进而建立了单层非均质地基一维固结模型。分析了起始水力坡降i0，非均质地基参数?、x、? 和p对非均质地基固结特性的影响。结果表明：考虑起始水力坡降后非均质地基中孔压消散速率变慢，地基沉降以及固结速率随之降低；固结速率与参数?、x成正比，而地基的最终沉降量与之成反比；参数? 越大，p越小，固结速率越快，但渗透系数仅改变地基的沉降速率，不会影响非均质土层的最终沉降量。

Analysis of consolidation of natural heterogeneous soils with a threshold hydraulic gradient

In practical engineering, the foundation is usually untreated, natural and heterogeneous. The phenomenon that threshold hydraulic gradient exists in clayey soil under low hydraulic gradient is gradually recognized. However, the consolidation model of heterogeneous foundations considering threshold hydraulic gradient is rarely reported. In this paper, based on seepage model considering threshold hydraulic gradient, the consolidation problem of heterogeneous foundation was studied, the change law of compressive modulus and permeability coefficient with depth under variable loads were obtained. One-dimensional consolidation model of single-layer heterogeneous foundation was established with an assumption that the compression modulus increases with depth, and the permeability coefficient decreases with depth. The influence of threshold hydraulic gradient i0, heterogeneous foundation parameter ?, x, ? and p on the consolidation characteristics of heterogeneous foundation were analyzed. The results show that, the rate of pore pressure dissipation becomes slower in heterogeneous foundation after considering threshold hydraulic gradient and settlement as well as consolidation rate of the foundation decreases accordingly. The consolidation rate is directly proportional to the value of ? and x while the final settlement of the foundation comes inversely proportional to them. The consolidation rate grows with the increase of ? and the decrease of p. However, the permeability coefficient may only change the settlement rate of foundation, which will not affect the final settlement of the heterogeneous foundations.