不同应力路径下饱和黏土耦合循环剪切特性

地基土单元体在波浪荷载的作用下将发生主应力轴连续旋转，这对土的强度和变形特性会产生显著的影响。针对饱和黏土，利用土工静力－动力液压三轴－扭转多功能扭剪仪进行了均等固结下的耦合循环剪切试验，着重研究了不同循环应力路径对应力-应变关系和强度特性的影响。试验结果表明，耦合循环荷载下黏土扭转剪切分量和正向偏差分量的应力-应变关系曲线与应力路径有关，且随着振动次数的增加逐渐疏松，割线模量 和 不断衰减，这与不固结不排水条件下的应力-应变关系曲线的变化规律明显不同；扭转剪切分量大的椭圆应力路径的动强度略小于正向偏差分量大的动强度。饱和黏土在不同应力路径下的力学特性的试验研究可以为建立复杂应力路径下的本构模型提供试验依据。

Study of coupling cyclic test of saturated clay under different stress paths

The cell of foundation soil is taken notable impact on dynamic deformation and dynamic strength behavior under rotation of principal stress axes by cyclic wave load. The apparatus for static and dynamic universal triaxial and torsional shear soil testing is employed to perform stress-controlled cyclic coupled vertical and torsional shear test by different cyclic stress paths. Through a series of tests on saturated clay, the dynamic deformation, stress-strain relationship and dynamic strength are systematically investigated under rotation of principal stress axes. It is found that stress-strain relation of shear stress and normal stress has obvious distinguishing between consolidated-undrained and unconsolidated-undrained coupling test by comparing the experiment data. Meanwhile, it is observed that stress-strain relationship curve gradually loosen and the secant modulus decayed as the cyclic number increased. Moreover, it is shown that the dynamic strength under major dynamic shear stress is less than the one under major normal stress by different elliptical stress paths. By conducting experiments on clay with changes in stress paths, the mechanical behavior can be investigated on which the establishment of proper constitutive model for soil is based.