循环荷载作用下高温-高含冰量冻土特性试验研究

为了研究高温-高含冰量冻土这种极不稳定土体的动力学特性,开展了固结围压为0.3、0.5、1.0、3.0、5.0MPa,控制温度为-0.5、-1.0、-2.0、-4.0℃、初始含水率为50%的高含冰量青藏线重塑冻土的动三轴试验。根据试验结果,提出了用广义的双曲线模型来描述动应力-应变关系,并且给出了模型参数预报关系式;基于动弹性模量和轴向应变之间的非线性关系,提出σ3=0.5MPa为临界围压。当围压大于0.5MPa时,动弹性模量随着动应变的增大呈减小的趋势;当围压小于0.5MPa时,动弹性模量随着动应变先增大后又减小;此外,动阻尼比随应变幅值和围压的增大而增大,随着温度的降低,动阻尼比变小。

Experimental study of characteristics of warm and ice-rich frozen clay under cyclic loading

In order to study the dynamic characteristics of warm and ice-rich frozen soil with the instability, a series of dynamic triaxial compressive tests on frozen clay of Qinghai-Tibet Railway, with the corresponding volumetric water content 50%, were conducted. Confining pressures are 0.3, 0.5, 1.0, 3.0, 5.0 MPa and temperatures are -0.5, -1.0, -2.0, -4.0℃. According to the tests results, the general hyperbolic model is proposed to describe the stress-strain relationships; and the prediction relationships of their parameters are provided. Based on the nonlinear relationship between dynamic elastic modulus and axial strain, the critical confining stress is figured out. The dynamic modulus decreases as the dynamic strain increases when the confining pressure is larger than 0.5 MPa. The dynamic modulus increases at first and then decreases as the dynamic strain increases when the confining pressure is below 0.5 MPa. Moreover, the damping ratio increases with increasing of shear strain amplitude or confining pressure; and with the decrease of temperature, the damping ratio becomes small.