循环荷载作用下珠海隧道饱和黏土软化试验研究

Experimental Study on the Softening of Saturated Clay of Zhuhai Tunnel under Cyclic Loading

通过对珠海隧道正常固结饱和粉质黏土和淤泥质黏土进行应力控制的循环三轴试验,研究循环荷载作用下土体软化情况。根据软化指数定义,得到土体软化指数曲线;分析了循环荷载过程中土体割线剪切模量发展规律;探讨动应力对土体软化的影响。结果表明:试样在每一循环次数中都存在临界屈服应变εp;循环次数较少时,土体刚度软化现象明显,随循环次数逐渐增加,土体刚度软化程度降低甚至不发生刚度软化;相对于加载波形为正弦波而言,半正弦波提高了土体刚度软化程度;动应力的提高增加了土体软化的程度。

To research the softening of clay under cyclic loading, cyclic triaxial tests with stress control were carried out on the normally consolidated saturated silty clay and mucky clay of Zhuhai tunnel. According to the definition of degradation index, the curve of clay＇ s degradation index was obtained. The development of secant shear modulus in each unload-reload loop was analyzed, and the influence of dynamic stress on the softening of clay was investigated. Results indicated that test sample had critical yield strain εp in every cycle and the degradation of stiffness was obvious when the cycle number was small. But with the increase of cycle number, the stiffness degradation reduced or even did not occur. Compared with sine wave, half-sine wave enhanced the degradation of stiffness. The in- crease of dynamic stress also intensified the softening of clay.