考虑涂抹区渗透系数变化的非饱和土砂井地基固结特性分析

ANALYSIS OF CONSOLIDATION OF FREE DRAINAGE WELL IN UNSATURATED SOIL WITH VARIABLE PERMEABILITY COEFFICIENT WITHIN SMEAR ZONE

在以往对非饱和土砂井地基固结理论研究中,均将涂抹区与非涂抹区土体渗透系数视为相等,这与实际工程并不相符。本文将考虑涂抹区土体渗透系数的变化,分析其对超孔隙气、水压力消散规律的影响。基于Fredlund一维固结理论以及Darcy定律和Fick定律,对有限厚度线弹性非饱和土砂井地基,在大面积均布瞬时荷载作用下,考虑涂抹区土体渗透系数的变化,利用Laplace变换并引入Bessel函数推导出Laplace变换下的解,再通过Crump方法编程实现Laplace逆变换得到超孔隙气压力、超孔隙水压力的半解析解。利用典型算例进行计算,分别得到在不同半径、不同涂抹区半径和不同涂抹程度的情况下,超孔隙气压力、超孔隙水压力随时间的变化规律。得出考虑涂抹作用时,超孔隙气、水压力的消散速度降低;涂抹区半径越大、涂抹程度越高速度越慢,反之消散越快。本研究丰富了非饱和土砂井固结理论,对非饱和土砂井固结特性的研究具有一定的工程参考价值。

The previous research theory of consolidation of unsaturated soil free drainage well foundation,both the permeability coefficient within the searched area and the non-searched area are considered equal. This assumption is not consistent with the actual engineering. The permeability coefficient can be variable within the smear zone in this paper. It gives the analysis of the regularity in pressure of excess pore water and air. It is based on Fredlund onedimensional consolidation theory,Darcy＇s law and the law of Fick. It examines finite thickness on the linear elastic unsaturated soil with sand drain foundation,and large area uniform transient load conditions. The change of permeability coefficient is considered in smear zone soil. It uses Laplace transformation and the introduction of Bessel function. It is accomplished by means crump Laplace inverse transformation. The excess pore-air and porewater pressure with semi-analytical solutions are got for unsaturated soil free drain wells. It calculates typicalexamples in different radius,smear zone radius and under the condition of different smear zone,and obtains air excess pore pressure and excess pore water pressure with the change rule of the time. The dissipation rates of air excess pore pressure and excess pore water pressure are much slower when the smear effect is considered. The greater the smear zone radius and the higher level of smear,then much slower and the more quickly conversely.This study enriches the theory of consolidation of unsaturated soil free drainage wells. The characteristics of the unsaturated soil consolidation of sand drain has certain reference value in engineering.