中国青藏铁路北麓河路基冻土动应变速率试验研究

Experimental study on dynamic strain rate of frozen soil from railway embankment of Qinghai-Tibet railway in China

基于低温动三轴试验,研究中国青藏铁路北麓河路基冻结粉质黏土在轴向分级循环荷载作用下的变形特征。在不同负温、频率、围压、含水率条件下,考察冻土试件轴向残余应变时程曲线,获得轴向动应变速率受动应力幅值影响大,并随应力比增大而增大,随负温降低、频率升高、含水率增大而减小,随围压增加而线性增大的结论;据此,提出采用幂函数拟合应力比、负温、含水率、频率与轴向动应变速率之间关系,并合理解释冻土特有的振融沉陷的成因机理。有利于合理预测青藏铁路等实际工程在交通荷载作用下由冻土动力残余变形而产生的沉降量,并对于进一步研究冻土路基列车行驶振陷问题具有重要意义,且为建立冻土疲劳模型积累基础试验成果。

Based on dynamic tri-axial tests at low temperature, the deformation behavior of frozen silty clay from railway embankment of Qinghai-Tibet railway was studied under stepped axial cyclic loading. Time history curves of residual strain of frozen soil were investigated under different negative temperatures, frequencies, confining pressures and water contents. Conclusions were drawn as follows： the dynamic load greatly affected axial strain rate; the axial strain rate linearly increased with the increasing of stress ratio and confining pressure, while decreased with decreasing of temperature, increasing of frequency and water content. According to the test data, an exponential function was brought forward to fit the relation between stress ratio, negative temperature, water content, frequency and axial strain rate. Then, the mechanism of settlement for frozen soil, caused by vibration exciting defreeze was explained. The study was helpful for the settlement prediction of projects like Qinghai-Tibet railway induced by residual deformation of frozen soil under traffic load. It was important to further study the railway embankment settlement caused by train steering, and the experimental data for fatigue model of frozen soil were also provided.