原生和次生各向异性对软黏土强度和变形特性影响研究

Effects of inherent and induced anisotropies on strength and deformation characteristics of soft clay

为更好地区分原生各向异性和次生各向异性对软黏土的强度和变形特性的影响,对原生各向异性明显的原状软黏土和基本消除了原生各向异性的重塑黏土,利用空心圆柱扭剪仪进行了两种不同b值下主应力轴偏转角不同的不排水定轴剪切试验。试验结果表明原状黏土的内摩擦角以及归一化强度都随着主应力方向的变化先减小后增加,而重塑黏土变化不明显,说明主应力方向变化引起的次生各向异性对重塑黏土强度影响较小。此外,原生各向异性对土体的应力应变开展有较大影响,对孔压开展模式基本无影响,但会影响孔压开展幅值。近似各向同性的重塑土基本消除了原生各向异性,因此该试验可为主应力轴旋转等复杂应力路径条件下的土体各向异性的深入研究提供较好的参考。

To better distinguish the effects of inherent and stress-induced anisotropies on deformation and strength, consolidated undrained tests on remolded and intact soft clay specimens are carried out using a hollow cylinder apparatus. The tests are conducted by maintaining a fixed principal stress direction with angle? from the vertical direction together with two different fixed values of the intermediate principal stress coefficient b. It is observed that both the friction angle and normalized strength decrease with the increase of ?, then have a small growth. However, the variance is not significant for different remolded clay species, so the stress-induced anisotropy caused by change of the principal stress direction has a smaller effect on the strength. Moreover, the inherent anisotropy has a great influence on the stress-strain characteristics and magnitude of pore pressure, and almost no effect on development mode of the pore pressure. Therefore, this study can serve as references for further study on the anisotropy of soft clay under the principal stress rotation.