复杂应力条件下饱和松砂孔隙水压力增长特性的试验研究

Experimental study on development pattern of shaking-induced pore water pressure of saturated loose sand under complex loading

针对福建标准砂Dr=30%,在三向非均等固结条件下,利用新研制的土工静力-动力液压三轴-扭转多功能剪切仪针对多种不同初始主应力变化方式进行了循环扭剪试验,讨论了初始主应力方向变化等初始固结条件对饱和松砂不排水条件下孔隙水压力变化规律的影响,对循环扭剪过程中主应力方向与中主应力系数的变化进行了分析,给出了孔隙水压力随循环次数的变化规律。结果表明:分别以最大孔隙水压力和液化破坏时循环次数归一化后的孔隙水压力比和循环次数比之间的关系依赖于循环剪应力幅值和初始主应力方向。而归一化后的孔隙水压力比与广义剪应变之间的关系和循环剪应力幅值、初始主应力方向无关,可以统一地采用双曲线模式表达,其中的两个待定参数依赖于初始主应力方向。

The soil static and dynamic universal triaxial and torsional shear apparatus is employed to perform experimental tests of Fujian standard sand with a relative density of 30% under different initial consolidation conditions subjected to undrained cyclic torsional shear loading. The effect of initial orientation of principal stress axes α(0) on the development pattern of shaking-induced pore water pressure of saturated loose sand is systematically investigated based on a series of soil tests. The variations of the orientation of principle stress ασ and the coefficient of intermediate principal stress b during cyclic shearing with the number of cycles N are examined. The development patterns of pore water pressure with the number of cycles are represented in different manners. It is shown that the relationship between the ratio of pore water pressure with initial mean effective stress and the ratio of the number of cycles with the number of cycles at failure depends on both the amplitude of cyclic shear stress and the initial orientation of principal stress while the relationship between the dimensionless pore water pressure and the generalized shear strain is almost independent of the amplitude of cyclic shear stress and the initial orientation of principal stress.