变荷载下基于指数渗流双层地基一维固结分析

Analysis of one-dimensional consolidation of double-layered soil with exponential flow considering time-dependent loading

在土中渗流服从指数形式的前提下,建立了变荷载作用下双层地基的一维固结控制微分方程。利用有限差分法求得孔隙水压力的数值解,并通过与解析解对比对其可靠性进行了验证。对双层地基在指数形式渗流时不同参数下的固结性状进行分析,结果表明:单面排水条件下,双层地基中上层土渗流指数的大小对固结速率起决定性作用,而下层土渗流指数大小对固结速率的影响很小;如果上、下两层土体的压缩性不同,则地基按变形定义的平均固结度和按孔压定义的平均固结度不再相等;地基中下层土与上层土的相对压缩性越低、相对渗透性越高,则地基的固结速率越快;增大压缩性小、渗透性高的土层相对厚度,会加快双层地基的固结速率。

Based on exponential flow law in soil,the governing equation of one-dimensional consolidation of double-layered soil considering time-dependent external loading is obtained.The finite difference method is adopted to obtain the numerical solution of excess pore water pressure;and then the reliability of numerical solution is verified by comparing numerical results with analytical results.Finally,consolidation behavior of double-layered soil with exponential flow law under various parameters is analyzed.The results show that the value of exponent in the upper layer largely determines the rate of consolidation,and that in the lower soil layer hardly influences the rate of consolidation in the case of single surface drainage.When compressibility of the upper soil layer is not equal to that of the lower soil layer,the average degree in terms of deformation can be not same as that in terms of pore pressure.The lower the relative compressibility,and the larger the relative permeability between the lower soil layer and the upper soil layer,the faster the rate of consolidation of double-layered soil.The rate of consolidation increases with increasing the relative thickness of soil layer with low-compressibility and high-permeability.