排水循环剪切条件下砂土体变特性试验研究

Experimental study of volumetric strain characteristics of sand subjected to drained cyclic shearing

利用土工静力-动力液压三轴-扭转多功能剪切仪,针对饱和福建标准砂,在各向均等与三向非均等固结条件下,进行了排水循环扭剪试验.通过试验讨论了初始主应力方向、相对密度和剪应变幅度对排水条件下饱和砂土体积变化特性的影响.研究表明:循环剪应变幅度和相对密度显著地影响饱和砂土体积变化规律,循环剪应变幅度越高,相对密度越大,越易于发生剪胀.在三向非均等固结情况下,饱和砂土在排水循环剪切条件下的体变特性密切地依赖于砂土的初始主应力方向.不同初始主应力方向时应力-应变关系表现出不同的变化模式,体积变化累积规律的具体模式取决于正应力水平与垂直平面上所存在的初始剪应力.

The soil static and dynamic universal triaxial and torsional shear apparatus is employed to perform drained cyclic torsional shear tests of saturated Fujian standard sand under initial conditions of isotropic consolidation or three-directional anisotropic consolidation. The effects of initial orientation of principal stress, relative density and shear strain amplitude on characteristics of volumetric strain induced under drained cyclic shear condition are examined on the basis of comparative tests. It is shown that the characteristics of volumetric change are noticeably affected by shear strain amplitude and relative density. The higher shear strain amplitude and the larger relative density, the heavier the dilatancy of sand subjected to drained cyclic shearing. It is indicated that the feature of volumetric change is closely dependent on the initial orientation of principal stress under initial three-directional anisotropic consolidation condition. The patterns of the stress-strain relation are associated with the initial orientation of principal stress and both variation mode of volumetric strain accumulation and dilatancy or/and contraction behaviour are related to the initial pre-shear stress imposed on the horizontal and vertical planes.