三轴循环加卸载条件下高含冰冻结砂土变形特性试验研究

Experimental investigation on deformation characteristics of ice-rich frozen silty sands under triaxial loading-unloading cycle

基于一系列同一温度、同一应变率、不同含水率和围压条件下的高含冰冻结粉质砂土的三轴循环加、卸载试验,开展了高含冰量冻结粉质砂土的能量耗散与剪切模量特性研究。试验结果表明:随着含水率的增加,冻土的塑性先增加,然后减小,并且30.6%的含水率可以作为一个塑性破坏点;随着剪应变的增加,偏应力的变化主导着能量耗散的变化,并且在试样变形过程中克服冰颗粒之间的作用所耗散的能量值很小;随着剪应变的增加,冻土的剪切模量一直减小,且小含水率条件下减小的速率会有一个明显的转折点,并且含水率对剪切模量的影响可分为3类。该研究结果可为高含冰冻土区工程设计中参数的选择提供重要的依据。

Energy dissipation and shear modulus variation of ice-rich frozen silty sand with different water contents are investigated in a comprehensive experimental program of triaxial loading-unloading cyclic tests under various confining pressures at the same temperature and strain rate conditions. The results show that the plasticity of frozen silty sand firstly increases and then decreases as the water content increases. The frozen soil presents mostly plastic failure mode with a water content threshold of 30.6%. The energy dissipation as shear strain increases is mainly induced by deviator stress variation, and less energy dissipation overcomes the effect between ice particles in the deformation process of frozen soil. Shear modulus always decreases as shear strain increases. The decreasing rate of shear modulus has an apparent change point at low water content.. Three types of effects of water content on shear modulus can be observed. These testing results can provide important implications for the parameter selection on engineering design in permafrost region with ice-rich soil.