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利用空心圆柱扭剪仪对杭州软黏土进行了一系列不排水试验,包括对原状软黏土在不同主应力方向上的定向剪切试验和主应力轴旋转试验以及对重塑软黏土的主应力轴旋转试验,主要研究不同应力路径下软黏土非共轴角的发展特性以及中主应力系数b、初始剪应力水平和次生各向异性对其非共轴特性的影响。试验结果表明,软黏土的非共轴特性虽与砂土存在相似之处,但又不尽相同。原状软黏土在定向剪切条件下的非共轴角均较小,并且与加载方向有关,然而受剪应变发展的影响,试样接近破坏时的非共轴角并不为0°;主应力轴旋转条件下,无论原状还是重塑黏土其非共轴角均随主应力方向角?增加而循环波动变化,且周期约为90°;非共轴角基本随中主应力系数b的增加而减小,但这种影响并不十分显著;剪应力水平对非共轴角的大小和发展趋势均存在一定的影响。对于重塑土的试验表明,软黏土的非共轴特性并不完全由土体的初始各向异性所决定,次生各向异性的影响也很大。
A series of undrained tests were carried out on Hangzhou soft clay using a hollow cylindrical torsional shear tester. The tests include directional shear test and principal stress axis rotation test of intact soft clay in different principal stress directions, Rotation test mainly studies the development characteristics of non-coaxial soft clay under different stress paths and the influence of the middle principal stress coefficient b, the initial shear stress level and the secondary anisotropy on the non-coaxial characteristics. The experimental results show that although the non-coaxial properties of soft clay have similarities with sand, they are not the same. The non-coaxial angles of intact soft clay under directional shear are small, and are related to the loading direction. However, due to the influence of shear strain, the non-coaxial angle near the failure of specimen is not 0 °. The principal stress Under the condition of axial rotation, the non-coaxial angle of non-original or remolded clay fluctuates with the increase of the direction angle of principal stress, and the period is about 90 °. The non-coaxial angle basically increases with the increase of middle main stress coefficient b Decrease, but this effect is not very significant; the level of shear stress has a certain impact on the size and development trend of non-coaxial angle. Experiments on remolded soil show that the non-coaxial nature of soft clay is not completely determined by the initial anisotropy of the soil, and secondary anisotropy is also greatly affected.