主应力轴持续旋转条件下饱和松砂的振动孔隙水压力特性

Dynamic pore water pressure behavior for saturated loose sand under condition of continuous rotation in principal stress direction

利用新研制的“土工静力-动力液压三轴-扭剪多功能剪切仪”,针对福建标准松砂,在三向非均等固结条件下,进行了能够模拟海洋波浪荷载作用下主应力轴连续旋转的循环耦合剪切试验。通过试验着重探讨了初始主应力方向、振动过程中主应力方向连续变化对不排水条件下砂土的振动孔隙水压力增长特性的影响。实验研究表明:在振动过程中主应力轴连续旋转的条件下,初始主应力方向对砂土的动孔压比与振次比之间关系具有显著的影响,随着初始大主应力与竖向之间夹角的增大,动孔压比的增长速度明显加快,具有较好的规律性;归一化孔压比与广义剪应变之间的关系基本上与初始主应力方向角和振动剪应力幅值无关。

The soil static and dynamic universal triaxial and torsional shear apparatus newly developed in Dalian University of Technology is used to perform the experimental tests of Fujian standard loose sand subjected to combined shear loading which can simulate the rotation in principal stress direction induced by ocean wave under the three-directional anisotropic consolidation condition. The effects of both initial orientation of the principal stresses and continuous rotation in principal stress direction during cyclic loading on built-up pattern of dynamic pore water pressure under undrained shear condition are investigated. It is shown through comparative experimental study that the initial orientation angle of major principal stresses a0 has a considerable influence on the relationship between the ratio of dynamic pore water pressure and ratio of cyclic number. With the increase of initial orientation angle of principal stresses, the rate of the building-up of dynamic pore water pressure will be notably increased. The rela- tionship between the dimensionless pore water pressure and the generalized shear strain is almost independent of the initial orientation of principal stresses and the amplitude of cyclic shear stress.