主应力轴旋转下K_0固结饱和粉质黏土孔压及变形特性试验研究

Experimental study on the pore pressure and deformation of saturated silty clay under K_0 consolidation and principal stress axis rotation

主应力旋转将加速孔压和塑性应变的累积,影响土体的力学特性。为研究主应力轴循环旋转对K_0固结饱和粉质黏土孔压和变形的影响,利用GDS-HCA试验系统开展了不同应力路径的K_0固结饱和粉质黏土不排水循环三轴试验和循环扭剪试验,研究了主应力轴循环旋转对K_0固结饱和粉质黏土累积塑性应变、孔压等动力特性的影响。结果表明:动剪应力幅值、心形应力路径所包围的面积、循环偏应力幅值等均随循环剪应力比和循环动应力比的增大而增大。试样未发生破坏时,K_0固结饱和粉质黏土的孔压比随着振动荷载作用次数的增加而增大;当试样发生破坏时,孔隙压力迅速消散,孔压比急剧下降。循环扭剪试验时试件产生的轴向累积塑性应变始终大于循环三轴试验产生的累积塑性应变,说明主应力轴循环旋转会加速试件轴向应变的累积。试件的累积塑性应变随循环剪应力比和循环动应力比的增大而增大。循环动应力比越大时,主应力轴旋转造成的轴向累积塑性应变差异越显著。在Monismith幂次函数模型的基础上,建立了主应力轴循环旋转条件时K_0固结饱和粉质黏土累积塑性应变方程,并对模型的可靠性进行了分析和验证。

The principal stress axis rotation will accelerate the accumulation of pore pressure and plastic strain and influence the mechanical properties of soil. The cyclic triaxial test and cyclic torsional shear tests were carried out by using GDS-HCA test system. The influence of continuous cyclic rotation of principal stress on the accumulative plastic strain and pore pressure of saturated silty clay under K0 consolidation were investigated. The amplitude of the dynamic shear stress, the area surrounded by the stress path of the heart, the amplitude of the cyclic stress amplitude increase with the increase of the cyclic shear stress ratio and cyclic stress ratio. The pore pressure ratio increases as vibration load cycles increasing before specimen damaged. The pore pressure dissipates rapidly after the specimen failure, and then the pores pressure ratio declines sharply. The axial cumulative plastic strain which produced by cyclic torsion shear tests is always greater than the cyclic triaxial tests. This indicates that the axial cyclic rotation of the principal stress axis will accelerate the accumulation of the axial strain of the specimen. The cumulative plastic strain increases with the increase of cyclic shear stress ratio and cyclic stress ratio. Large cyclic stress ratio results in significant cumulative plastic strain caused by the rotation of the shaft. The accumulated plastic strain of saturated silty clay under K0 consolidation and the cyclic rotation conditions of principal stress is established basing on the Monismith power function model. The reliability of the model is analyzed and verified.