冻融循环作用下冻结冰碛土剪切特性

Shear characteristics of frozen moraine soil under freeze-thaw cycle

针对中国西南某高速铁路昌林段沿线冰碛土的特殊环境,通过相似级配法对冻结冰碛土进行固结排水直剪试验,研究冻融循环次数与初始含水率对冻结冰碛土力学性能的影响。结果表明:冻融循环次数是影响冻结冰碛土抗剪强度的重要因素,而初始含水率影响不大;该土样的抗剪强度与冰饱和度密切相关,在初始含水率为8%~12%时存在最大值;冻融循环致使土体强度持续降低,较低初始含水率时的强度损失与冻融次数基本呈线性关系,高初始含水率时前期冻融循环对土体的破坏作用更为明显;2个因素对土体内摩擦角的影响不大,对黏聚力的影响显著。引入综合性参数(K),建立了黏聚力与K值的指数函数模型,回归分析结果表明,该模型能够较好地描述K值与黏聚力之间的关系。

For the special environment of moraine soil along the Changdu-Linzhi section of a high-speed railway in southwest China,the effects of freeze-thaw cycles and initial water content on the mechanical properties of frozen moraine soil were studied through consolidating and draining direct shear test by using similar gradation method.The results show that the number of freeze-thaw cycles is an important factor affecting the shear strength of frozen moraine soil,but the initial water content has little effect.The shear strength of the soil sample is closely related to the ice saturation,and the maximum value exists between the initial water content of 8%and 12%.The strength of soil decreases continuously due to freeze-thaw cycles,and the strength loss is basically linear with the number of freeze-thaw cycles when the moisture content is lower,and the damage effect in the early stage of freeze-thaw cycles on the soil is more obvious when the moisture content is higher.The two different conditions have little effect on the internal friction angle and significant effect on the cohesion of soil.By introducing the comprehensive parameter K,the exponential function model of cohesion and K value is established.The regression analysis shows that this model can better describe the relationship between K value and cohesion.