饱和黏土剪切变形与强度特性试验研究

针对由真空抽吸制样技术制备的饱和重塑黏土,在0.000 2～0.1 mm/s剪切速率范围内.进行了多组应变控制的UU和CU三轴剪切试验,通过对比试验系统地探讨了围压和剪切速率对饱和黏土的应力-应变关系及其强度特性的影响.试验结果表明,饱和黏土的应力-应变关系在低剪切速率下发生应变强化.而在高剪切速率下出现峰值强度和应变软化,不排水强度随剪切速率的增加而增大,增长幅度可达70%.但当应变超过10%以后的最终残余强度趋于相等.同时试验还发现.在UU试验条件下黏土应力-应变关系与强度特性不受围压的影响,而受剪切速率的影响较为显著.通过归一化.建议了不排水强度与剪切速率之间的线性拟合公式.在确定拟合参数以后.在一定的剪切速率范围内可以同时估计UU和CU试验条件下各剪切速率下的强度.

Experimental study of shear and strength behavior of saturated clay

A series of undrained (UU) and consolidated-undrained (CU) triaxial tests are carried out to systematically investigate the effect of shearing rate and confining pressure on stress-strain relation and strength behavior of saturated clay. Shearing rate is controlled to vary between 0.000 2 and 0.1 mm/s. Experimental data indicate that strain hardening appears at low shearing rate while strain softening occurs after peak strength at high shearing rate. Nevertheless, the deviatoric stress at different shearing rates will tend to be identical after the strain exceeds 10%. Undrained strength of the clay increases with the increase of shearing rate. The increase of shear strength of about 70% may be attained. In addition, it is revealed that stress-strain relation and strength behavior are mainly affected by shearing rate. However, they are almost independent on confining pressure under the condition of UU tests. An empirical linear relation which correlates shear strength and shearing rate is established and can be used to estimate the undrained strength at different shearing rates and under UU or CU condition.