考虑非达西渗流的单层非均质地基固结分析

Analysis on the consolidation of non-homogeneous soil with non-Darcian flow law

各类地质作用形成的非均质粘性土地基在工程界中广泛存在,同时非均质粘性土中渗流在低水力坡降下会出现非达西渗流的现象。但考虑非达西渗流的非均质粘性土地基一维固结理论尚不完善,应用达西定律计算低水力坡降情况下非均质粘性土中的渗流,会存在较大的误差。因此通过假定粘性土压缩模量随深度线性增加且渗透系数随深度指数减小来考虑地基的非均质性,并考虑实际中变荷载作用建立了非达西渗流下非均质地基固结模型。在此基础上,运用有限差分法获其数值解,并与相应的达西渗流解析解进行对比,验证了本文解的正确性;分别研究了非达西渗流参数m、i_1和非均质地基参数α、μ、p对土体孔压、地基沉降、地基平均固结度的影响。结果表明:m和i_1值越大,非均质地基中孔压消散越慢,土体固结速率也随之变慢;非均质粘性土地基参数的影响各异,α越大或μ越大、p越小的情况下,固结速率越快,且随着α值增大,非均质土体的最终沉降值越小;而m、i_1、μ、p对地基最终沉降量没有影响。非达西渗流和地基的非均质性都会影响土体的固结性状,故此两者在固结计算过程中不可忽略。

The heterogeneity clayey soil generated by various geological actions existed widely in engineering.Meanwhile, non-Darcian seepage phenomenon in clayey soil under low hydraulic gradient also had been recognized gradually. However, the consolidation theory of heterogeneous clayey soil with non-Darcian flow law was rarely reported. In present contribution, non-Darcian flow law of heterogeneous soil under the low hydraulic gradient is considered with the assumption that the compression modulus of heterogeneous foundation increases linearly with depth while the permeability coefficient decreases exponentially with depth. The consolidation model of heterogeneous clayey soil with non-Darcian flow law is established by considering the actual change of external load. The finite difference method is adopted to obtain the numerical solution, and the reliability of the numerical solution is verified by comparing to the analytical solutions of heterogeneous soil with Darcy's flow law.Finally, influences of the parameters m、i_1 of non-Darcy flow law and parameters α、μ and p of non-homogeneous soil on the dissipation of excess pore pressure, the settlement and the average degree of consolidation are analyzed.Results obtained show that the greater the values of m、i_1 are, the slower the consolidation rate of soil layer is; the greater the heterogeneity parameter α is, the faster the consolidation rate of soil layer is; α is the main factor which affects the final settlement; the greater the value of α is, the smaller final settlement will be; the greater μ is and the smaller p is, the faster the consolidation rate of soil layer is. However, parameters m、i_1 and heterogeneityparameters μ and p have no effect on the final settlement. Non-Darcian flow law and the heterogeneity of the foundation affect the consolidation behavior, therefore, both of them cannot be neglected in the consolidation calculation of soft clay layer.