动力荷载长期作用下冻土振陷模型试验研究

Experimental research of vibration excited subsidence of frozen soil under long-term dynamic loads

基于低温动三轴试验资料,研究了青藏铁路北麓河粉质黏土在往返长期加荷作用下的变形特征。在不同温度、动应力幅、频率、围压条件下考察冻土轴向残余应变与振次的试验关系曲线,建立了冻土振陷模型,并讨论了模型参数及其影响因素。研究表明,(1)模型参数受拟合所采用的振次水平影响较大,参数B(黏塑流蠕变率)随振次的增加而迅速减小,参数C(蠕变衰减系数)随振次的增加而迅速增大;(2)除迅速破坏的试件外,当振次达到一定临界值以后,B、C两参数都逐渐趋于稳定;相同振次水平下B、C参数均随温度升高、动应力幅值增大、围压增高而增大,随频率的增加而减少,且频率大于6Hz时对参数影响很小。此项研究对于合理预测动力荷载长期作用下由冻土残余变形而产生的沉降量具有重要意义,且为冻土动力学研究积累基础试验成果。

Based on dynamic triaxial test at low temperature, deformation behavior of silty clay sampled from Beiluhe section of Qinghai-Tibet Railway under long-term cyclic loading is studied. At different negative temperatures, frequency, confining pressure and water content, relation curves between residual strain and vibration times of frozen soil are investigated; vibration excited subsidence model is built; and its parameters along with influential factors are discussed. The results demonstrate that the parameters are deeply influenced by adopted vibration times, among which, B（viscous, plastic, rheological and creep rate） decreases and C（creep regression coefficient） increases sharply with increasing of vibration times; with the exception of quickly destroyed specimens, both of the two parameters tend to be stable when vibration up to critical times; under the same vibration times, both of the two parameters decrease with rising of temperature, increasing of dynamic stress magnitude or chamber pressure, and are influenced little as vibration frequency higher than 6Hz. The work makes a contribution to properly predicting of settlement induced by residual deformation of frozen soil under long-term dynamic loads and provides experimental data to further research on dynamic characteristics of frozen soil.