含应力旋转路径对软黏土小应变刚度影响试验研究

利用配备高精度局部位移传感器的空心圆柱扭剪仪对杭州软黏土开展了系列应力旋转路径条件下的试验研究,包括:大主应力沿不同角度的定向剪切,不同剪应力水平下大主应力单纯连续旋转后定向剪切以及大主应力往复循环旋转后定向剪切3类典型应力路径,并考虑了中主应力系数及剪应力水平的影响。重点分析应力旋转路径对软黏土小应变刚度特性的影响。主要结论有:在不同的复杂应力条件下软黏土的刚度均受应变大小的影响,应变小于0.01%时软黏土的刚度很大,在0.01%~0.1%范围内刚度迅速衰减;在定向剪切条件下剪切方向对软黏土小应变剪切刚度的影响并不明显,而中主应力系数的影响比较显著;在主应力单纯旋转阶段软黏土会因不同的剪应力幅值产生不同程度的应变累积,继而对土体的小应变刚度的影响程度也不同;主应力往复循环旋转虽然也会产生前期累积应变,但土体在后期定向剪切阶段的初始刚度并未显著衰减,说明应力旋转模式对小应变刚度也有很大影响。

Experimental study on influence of stress rotation on small-strain stiffness behavior of soft clay

A series of principal stress rotation tests are carried out on soft clay using a hollow cylinder apparatus equipped with high censers. The stress paths with fixed principal stress directions, pure principal stress rotation and cyclic principal stress rotation are studied. The influences of the intermediate principal stress parameter (b) and shear stress level (q) are taken into consideration. The effect of stress rotation on the small strain stiffness of soft clay is studied in particular. The test results indicate that the stiffness of soft clay is affected by the magnitude of strain under complex stress condition. The stiffness is relatively higher when the strain is smaller than 0.01%, and the stiffness decreases quickly during 0.01%~0.1%. The influence of shearing direction on the small strain stiffness is unobvious, while the influence of b is obvious. The influence of the pure principal stress rotation on the small strain stiffness of soft clay is dependent on the strain induced by the pure principal stress rotation. Strain is also accumulated during cyclic principal stress rotation, while the stiffness of soft clay is less influenced during fixed direction shearing, which indicates that the mode of the principal stress rotation also has significant effect on the small strain stiffness of soft clay.