真三轴条件下Q_3原状黄土的吸力变化特性研究

Suction changes of intact Q_3 loess based on true triaxial tests

为了研究非饱和土在复杂应力作用下的基质吸力变化特性,利用非饱和土真三轴仪,对不同初始基质吸力的非饱和原状黄土进行了常含水率等向固结和不同中主应力比值b应力路径的剪切试验,研究了非饱和原状黄土在真三轴应力条件下的吸力变化特性。研究结果表明:等向固结过程中吸力随着时间的增大而减小,且随着初始吸力和净平均应力的增大,吸力的减小速率越快,吸力变化量越大;等向固结完成后吸力小于初始吸力。剪切过程中吸力随时间的增大呈微小降低或保持不变后较快上升趋势,随着净围压或b值的增大,吸力上升段增长较快,吸力增量越大:剪切完成后吸力大于等向固结完成后的吸力。常含水率真三轴加载作用下黄土的基质吸力变化与净围压和中主应力比值b的不同组合密切相关。

To investigate the variation of matric suction of unsaturated soils under complex stress conditions, a series of isotropic consolidation and shear tests along the stress paths of different intermediate principal stress ratios b with constant water content is performed on intact loess with various initial suctions by using unsaturated soil true triaxial apparatus. The characteristics of suction of unsaturated intact loess under the condition of true triaxial stress are studied. The results show that suction decreases with the time in the process of isotropic consolidation. Suction decreases faster and the variation of suction is larger with the increase of initial suction and net mean stress. The suction after the completion of isotropic consolidation is smaller than the initial suction. The suction in the process of shear declines little or remains unchanged then rise rapidly with the time. The suction rising segment grows rapidly and the suction increment is larger with the increase of the net confining stress or ratio b. The suction after the completion of shear is greater than the suction after the completion of isotropic consolidation. The changes of the matric suction are closely related to the different combinations of the net confining pressure and the ratio b under the action of true tri-axial loading.