线性卸荷作用下软土超孔隙水压力变化规律分析

Analysis of the evolution of excess pore water pressure in soft soil under linear unloading

目前对软土在卸荷下的固结变形研究主要集中在瞬时卸荷。为明确线性卸荷作用下软土固结变形的规律,通过太沙基一维固结理论与有效应力原理的方法,研究了软土地基在任意卸荷速率下一维固结方程的通解,并求解了线性卸荷下固结方程的解析解。结果表明,线性卸荷作用下软土地基产生的负超孔压可以分成增长期、快速消散期和缓慢消散期3个阶段;卸荷速率影响负超孔压的增长路径和消散速率而卸荷量影响最大负孔压值,最大负超孔压值与卸荷量近似成线性增长关系;最后结合工程实例进行对比分析,发现卸荷导致的负超孔压值和其消散速率都在卸荷结束的时刻最大,同时理论计算结果及变化规律与实测有较好的吻合性。

At present,the research on the consolidation deformation of soft soil under unloading mainly focuses on the instantaneous unloading.In order to clarify the evolution of consolidation deformation of soft soil under linear unloading,through the one-dimensional consolidation theory of Terzaghi and the principle of effective stress,an effective method is proposed to study the general solution of the soft soil foundation under the arbitrary unloading rate and solve the analytical solution of the consolidation equation under linear unloading.The results show that:1)the negative excess pore pressure generated in soft soil foundation under linear unloading can be divided into three stages:growth period,rapid dissipation period and slow dissipation period;2)unloading rate affects the growth path and dissipation rate of negative excess pore pressure;3)and unloading affects the maximum negative excess pore pressure with the unloading amount approximately linearly increasing.Finally,taking engineering examples for comparative analysis,it is found that the negative excess pore pressure and its dissipation rate induced by unloading are the highest at the end of unloading.The theoretical results with evolution trends are in good agreement with field measurements.