复杂应力条件下饱和砂土单调剪切特性的试验研究

利用土工静力-动力液压-三轴扭转多功能剪切仪，针对相对密度为30 %的福建标准砂，进行了复杂初始固结条件下应力路径变化的应力控制式单调排水与不排水剪切试验。控制试验过程的平均主应力保持不变，变化中主应力系数和主应力方向，分别探讨在不同排水条件下中主应力系数和主应力方向对饱和砂土剪切特性的影响。通过对比表明：与排水条件无关，中主应力系数对归一化的应力-应变关系具有影响，但对体变或孔压的影响并不明显。初始条件相同，偏应力比随中主应力系数的增大而降低。主应力方向的影响同样显著，排水试验的主应力方向角不同时应力-应变关系所表现出的变化规律取决于水平面与竖直面上受到的剪应力作用。不排水试验的峰值有效偏应力比随着主应力方向角的增大而减小。

Experimental study of monotonic shear behaviors of saturated sands under complex stress conditions

Various stress-controlled drained and undrained monotonic shear tests on the Chinese Fujian standard sand of relative density 30 % under complex initial consolidation conditions with different stress paths are conducted by using the soil static and dynamic universal triaxial and torsional shear apparatus. The average principal stress is unchanged in the process of tests. The coefficient of intermediate principal stress and orientation of principal stress are changed so that their influences on shear behaviors of saturated sands under different drainage conditions are respectively probed. It is shown by comparison that coefficient of intermediate principal stress influences the stress-strain normalization relationship, but does not have obvious effect on volumetric deformation as well as pore-water pressure. Under the same initial condition, the deviator stress ratio decreases with the increase in coefficient of intermediate principal stress. The above-mentioned phenomena do not relate to the drainage condition. Orientation of principal stress also has remarkable influence on monotonic shear features of sands. In drained tests, variation pattern of stress-strain relationship which is associated with the orientation of principal stress depends on shear stresses on horizontal plane and vertical plane. In undrained tests, the effective deviator stress ratio attained at peak state decreases gradually with the increase in orientation angle of principal stress.