为研究中主应力系数和大主应力方向角对各向异性软黏土变形特性的影响，利用GDS空心圆柱扭剪仪对温州原状软黏土进行了一系列不同中主应力系数和大主应力方向角的排水定向剪切试验。试验过程中在大主应力方向角和中主应力系数不变的条件下，逐渐增加剪应力直至试样破坏。分析了中主应力系数和大主应力方向角对温州原状土偏应力与大主应变关系、体应变、中主应变和小主应变与大主应变关系的影响。试验结果表明：试样的应力-应变关系在中主应力系数和大主应力方向角不同时表现出明显的各向异性。当中主应力系数为0.00和1.00时，大主应力方向角对应力-应变关系的影响较小；而当中主应力系数为0.50时，应力-应变关系中的割线剪切模量随大主应力方向角变化明显。当大主应力方向角为30°时，随着中主应力系数从0.00增加到0.50，中主应变由压缩状态变为拉伸状态；当大主应力方向角为45°时，随着中主应力系数从0.00增加到1.00，中主应变由压缩状态变为拉伸状态。

In order to evaluate the influence of intermediate principal stress and major principal stress direction on the drainage-induced deformation of natural soft clay, a series of drained directional shear tests is carried out on Wenzhou natural soft clay with different intermediate principal stress coefficients and different major principal stress directional angles, using a GDS hollow cylinder torsional shear apparatus. During the tests, the shear stress is increased gradually until the specimens failed, while the major principal stress direction and the intermediate principal stress coefficient remain unchanged. The influences of intermediate principal stress coefficient and major principal stress direction are discussed on the relationship between the deviator stress and major principal strain, and the relationships between the major principal strain and the intermediate principal strain, minor principal strain and volumetric strain. It is found that the anisotropy expressed by the stress-strain relationship is affected by different intermediate principal stress coefficient and major principal stress direction. When the intermediate principal stress coefficient remains as 0.00 and 1.00, the influence of major principal stress direction on stress-strain relationship is insignificant. However, when the intermediate principal stress coefficient reaches 0.50, the secant modulus in stress-strain relationship is significantly influenced by major principal stress direction. When the major principal stress direction angle is 30°, the intermediate principal strain changes from compressive state to tensile state as the intermediate principal stress coefficient increase from 0.00 to 0.50. When the major principal stress direction angle is 45°, the intermediate principal strain changes from compressive state to tensile state when the intermediate principal stress coefficient increases from 0.00 to 1.00.