定向剪切应力路径下冻结黏土变形特性试验

为研究复杂应力路径下冻土的强度与变形特征，采用冻土空心圆柱仪（FHCA-300）对不同负温状态下的饱和冻结黏土开展定向剪切试验，基于不同剪切方向下冻结黏土的轴向和扭剪分量的应力-应变关系，探讨土样的剪切变形特征、各向异性属性以及剪切带的演变规律，并考察温度、大主应力方向角、平均主应力以及中主应力系数等因素对冻结黏土强度的影响。结果表明：平均主应力p值对冻结黏土的应力-应变关系影响显著，尤其是p=4.5 MPa时具有较高的剪切强度，且该值可能为压融临界p值；大主应力方向变化会诱发冻结黏土的各向异性，随着大主应力方向角的增加，冻结黏土剪切强度逐渐降低，并有明显的剪切带产生；中主应力系数的增加使得轴向强度有逐渐降低的趋势，但对剪切强度影响不明显；随着温度的降低，冻结黏土强度逐渐增大，试样发生脆性破坏并出现剪切破裂面，其剪切强度主要取决于冰颗粒和土颗粒的胶结力。

Experimental study of deformation characteristics of frozen clay under directional shear stress path

To study the strength and deformation characteristics of frozen clay under complex stress path, a series of directional shear tests on saturated frozen clay is conducted under different negative temperature conditions by using dynamic hollow cylinder testing apparatus of frozen soils (FHCA-300). Stress-strain curves of the axial and torsional shear components for frozen clay are analyzed under different shear directions. The shear deformation, anisotropy and shear band characteristics are discussed. And the effects of temperature, angle of major principal stress direction, mean principal stress and coefficient of intermediate principal stress in the strength and deformation behaviors of frozen clay are explored. The test results indicate that the value of the mean principal stress p has a significant effect on the stress-strain curves of frozen clay. When p=4.5 MPa, the frozen clay has a major shear strength and this stress value (the mean principal stress) may be the critical value of pressure melting. The anisotropy of frozen clay may be induced by the change of major principal stress direction. Shear strength decreases versus the increase of angle of major principal stress direction. The axial strength decreases with the increase of the coefficient of intermediate principal stress, but the effect of the coefficient on the shear strength is neglect. With the decrease of temperature, the strength of frozen clay increases gradually. Meanwhile, the samples produce brittle failure, and a shear failure surface appears and develops. The shear strength of frozen clay depends mainly on the cementation force between soils and ice particles.