饱和黏土循环剪切强度与变形特性的试验研究

Experimental study on cyclic shear strength and deformation behavior of saturated clays

利用土工静力-动力液压三轴-扭转多功能剪切仪,在不固结、不排水条件下对黏土的单调和循环剪切应力-应变关系与剪切强度特性进行了研究。单调剪切试验表明剪切强度随应变速率的增加而增大,在双对数坐标下,剪切强度与应变速率之间近似地符合线性关系;循环剪切试验表明对于某一给定的初始剪应力,循环剪切强度大小是循环软化效应和应变速率效应共同作用的结果,结合单调剪切强度应变速率之间的对应关系,提出了近似消除速率效应的循环剪切强度归一化方法,通过归一化表明,不同循环次数的循环剪切强度与初始剪应力之间的试验数据点分布在一个狭窄区域内,通过一个二次方程即可拟合表示。以此为基础,提出了循环剪切强度的简便确定方法,可减少海洋地基稳定性分析中的试验工作量。

The static triaxial-dynamic triaxiat-torsional shear multi-function testing apparatus designed for soil experiment is used to carry out the monotonic shear test and cyclic shear test for clay under the conditions of unconsolidated and undrained to investigate the cyclic shear stress-strain relationship and shear strength behavior. The monotonic shear test result shows the shear strength increases following the increase of the strain rate and the relationship between strain rate and monotonic shear strength in log-log plotting is approximate to linear. The cyclic shear test result shows that the cyclic shear strength is affected both by cyclic softening effect and strain rate effect. A normalized approach for determining the cyclic shear stress with the effect of stain rate diminished is suggested. By means of normalization the experimental data in plotting of relationship between cyclic shear strength and initial shear stress are gathered in a narrow strip and a quadratic equation for fitting is proposed. On this basis, cyclic shear strength of saturated clay can be simply determined.