杭州软黏土非共轴特性的试验研究

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。

Experimental study of non-coaxiality of Hangzhou soft clay

A series of undrained tests is carried out on Hangzhou soft clay with hollow cylinder apparatus. The stress paths which include shearing test under different-fixed principal stress directions for the intact soft clay and principal stress rotation for intact and remolded soft clay are designed to study the non-coaxial development behavior of soft clay as well as the influence of intermediate principal stress parameter b, initial deviatoric stress and induced anisotropy on non-coaxiality. The results show that the non-coaxiality of soft clay is similar to that of sand, but they are far from identical. The non-coaxial angle is quite small in fixed shear tests; and it is dependent on the loading directions; however, affected by the development of deviatoric stain, the non-coaxial angle is not 0° when the specimen is close to failure. Regardless of intact soft clay or remolded soft clay, the non-coaxial angle fluctuates with the increase of principal stress orientation α, of which the cycle period is 90°. The non-coaxial angle basically decreases with the increase of coefficient of intermediate principal stress b, but this effect is not quite remarkable. The deviatoric stress has certain effect on the angle of non-coaxial as well as its development trend. As to the test of remodeled soft clay, it shows that the non-coaxiality is not only entirely determined by the inherent anisotropy, the induced anisotropy also has a great impact.