高温冻土剪切力学特性试验研究

Experimental study on shear mechanical properties of warm frozen soil

利用重塑土的直剪试验,探讨-2℃条件下青藏地区3种不同土性(粉质黏土、粉砂、细砂)冻土的直剪力学特性。结果表明:高温冻土剪切特性与土性、密度、含冰量密切相关;剪切位移-剪应力曲线在相对密实条件下呈应变软化型,而在相对松散状态下呈应变硬化型;不同密实条件下粉质黏土的内摩擦角随含冰量的增加表现为先降低后增加,而细砂的内摩擦角随含冰量的增加而增加;在相同含冰量条件下粉质黏土、细砂的内摩擦角随密度的增加而增加;粉砂在不同密实条件下内摩擦角随密度的变化规律与粉质黏土类似,但在相同含冰量条件下内摩擦角随密度的变化规律与粉质黏土、细砂相反;-2℃条件下不同土性高温冻土黏聚力随密度、含冰量变化的规律不明显。高温冻土地区的工程建设应根据土性、密度、含冰量情况合理选取抗剪强度指标。

The direct shear characteristics of warm frozen soil with three different soil properties(silty clay,silty sand and fine sand)from Qinghai-Tibet Plateau under the condition of-2℃are studied by using the direct shear test of remolded soil.It shows that the shear characteristics of warm frozen soil in the study area are closely related to soil property,density and ice content and the shear displacement-shear stress curve shows strain softening under relatively dense condition and strain hardening under relatively loose condition.During the experiments,the internal friction angle of silty clay decreases first and then increases with the increase of ice content under different compacting conditions,while the internal friction angle of fine sand increases with the increase of ice content.Furthermore,the internal friction angle of silty clay and fine sand with same ice content increased along with the increase of density.The change of internal friction angle with density of silty clay is similar to that of silty clay under different density conditions,but the change of internal friction angle with density and with the same ice content is opposite to that of silty clay and fine sand.Therefore,the cohesive force of warm frozen soil with different soil properties changes with density and ice content at-2℃.For the construction of high-temperature permafrost regions,the shear strength indexes should be selected reasonably according to soil properties,density and ice content.