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采用空心圆柱扭剪仪对原状饱和软黏土进行了纯主应力轴旋转应力路径的循环不排水试验,加载过程中维持平均应力、广义剪应力和中主应力系数不变。观测了孔隙水压和各应变分量在循环加载过程中的变化特性,着重探讨了中主应力系数及广义剪应力对变形刚度以及非共轴特性的影响规律。主应力偏转的循环剪切路径下,存在扭转剪切和轴向剪切两种不同的循环应力应变响应。试验结果表明:循环加载路径下饱和软黏土的孔压及应变产生累积效应,应力应变刚度呈现各向异性弱(强)化效应,而应变增量呈现显著的非共轴性;中主应力系数b影响特性表现为,b值越大则刚度弱化越显著。试验观察还发现,剪应力水平较低时循环变形刚度表现为强化,非共轴角趋于增大;反之,剪应力水平较高时,伴随着循环弱化,非共轴角趋于减小。
Hollow cylindrical torsional shear instrument was used to test the undrained cyclic undrained cyclic stress path of pure saturated clays. The average stress, the generalized shear stress and the middle principal stress coefficient were kept unchanged during the loading process. The variation characteristics of pore water pressure and strain components during cyclic loading were observed. The influences of middle principal stress coefficient and generalized shear stress on deformation stiffness and non-coaxiality were mainly discussed. Under the cyclic shear path of principal stress deflection, there are two different cyclic stress-strain responses of torsional shear and axial shear. The experimental results show that the pore pressure and strain of the saturated soft clay have a cumulative effect under the cyclic loading path, the stress-strain stiffness shows weak anisotropy (strong) effect, and the strain increment shows significant non-coaxiality. The medium principal stress coefficient b The influence characteristic is that the greater the b value is, the more significant the rigidity weakening is. The experimental observations also show that the cyclic deformation stiffness is enhanced and the non-coaxial angle tends to increase when the shear stress is low. Conversely, when the shear stress is high, the non-coaxial angle tends to decrease along with the weakened circulation.