饱和软粘土中沉桩后桩周土体固结分析

假定沉桩过程是一个平面应变圆孔扩张问题, 采用了修正剑桥模型, 给出了软粘土中沉桩过程后初始时刻超孔隙水压力沿桩径分布的解析函数, 并与Cao 等人的数值解以及Gibson 提出的公式进行了比较。根据土骨架的弹性位移特性以及水流的连续性条件, 得到了桩周土体固结的控制方程。运用分离变量法并结合边界条件以及初始条件得到了桩周土中超孔隙水压力消散的级数解答, 该解答可以作为孔压静力触探反求固结系数的一个理论依据。通过2 个算例分析了土体的应力历史以及刚度对桩侧超静孔压消散的影响;算例分析表明, 随着超固结比的增大, 归一化后的塑性区半径以及桩侧超孔隙水压力均在减小;桩侧的超静孔压消散前期较快, 后期较慢。

CONSOLIDATION ANALYSIS AROUND A DRIVEN PILE IN SATURATED CLAY

A distribution formula of initial excess pore pressure is proposed with a modified cam-clay model and assumptions of plane strain conditions. This formula is compared with the adequate numerical method proposed by Cao and the formulation by Gibson. The governing equation of consolidation is derived, based on the elastic deformation of soil skeleton and continuity of fluid water. Thus an analytical solution is obtained through a variable separation approach combining established initial and boundary conditions, and this solution can be used as a theoretical foundation of deducing coefficients of consolidation in a pressuremeter test. A parametric study of dissipation of excess pore pressure is made, considering the effect of stress history and rigidity index. The results indicate that the normalized plastic radius and excess pore pressure decrease as the increasing of overconsolidation ratios. The dissipation of excess pore pressure around a pile runs fast at its early stage while slow at its late stage.