考虑主应力方向变化的原状黏土强度及超静孔压特性研究

针对许多实际岩土工程问题中,土体所受应力路径主应力方向会旋转变化的特点,采用空心圆柱仪(HCA)对主应力轴方向突变和连续旋转条件下杭州典型原状黏土的强度和孔压特征进行研究。试验表明:土体强度主要受原生各向异性影响,试样在破坏时的主应力作用方向以及中主应力参数是影响土体强度的主要因素,而主应力轴旋转对于强度则无显著影响;试样无论是否经历主应力轴旋转,在破坏时都会有显著的剪切带产生,同时剪切带平面与大主应力作用方向的夹角基本保持一个常数;主应力轴旋转会引起土中孔压积累,积累程度受主应力轴转幅及旋转时剪应力幅值、剪应力水平支配。这部分孔压增量较之主应力方向固定不变剪切产生的极限孔压而言不能忽略。

Research on strength and pore pressure of intact clay considering variation of principal stress direction

In many practical geotechnical problems,soils are always subjected to the stress path involving the principal stress rotation.A hollow cylinder apparatus(HCA) was used to study the properties on strength and pore pressure of typical Hangzhou intact clay during the variation of principal stress direction.It was revealed that due to the inherent anisotropy in structure of soils,the strength was greatly affected by the direction of the major principal stress and the parameters of intermediate principal stress but the influence of principal stress rotation(PSR) was not ecident.Shear band formed when samples failed no matter whether PSR had happened or not,meanwhile the angle between the shear band plane and direction of the major principal stress nearly kept constant.PSR could cause pore pressure accumulation due to PSR which couldn’t be neglected as compared with limiting pore pressure caused by shear with fixed stress direction,and the quantity of accumulation was decided by amplitude of rotation,value of shear stress and shear stress level.