基于冻融-干湿作用的非饱和重塑黄土强度试验

Experiment on strength of unsaturated remodeled loess based on freeze-thaw and dry-wet effects

冻融循环和干湿交替作为两种典型的风化作用,对土体强度有着显著的影响.为了探讨二者对土体强度影响的差异及吸力机制,对不同含水量的非饱和重塑黄土开展冻融及冻融干湿耦合作用下的直剪试验,同时测试基质吸力.结果表明:冻融条件下,黏聚力随冻融次数呈指数函数减小,内摩擦角随冻融次数呈指数函数增大,抗剪强度随冻融次数增加而增大.冻融干湿耦合下,黏聚力和内摩擦角均随着冻融干湿耦合次数呈指数函数减小,抗剪强度随冻融干湿耦合次数增加而减小;干湿路径对抗剪强度具有一定的影响,先吸湿后脱湿的抗剪强度和强度参数大于先脱湿后吸湿的抗剪强度和强度参数.基于试验数据分别给出黏聚力和内摩擦角随冻融-干湿耦合次数变化的定量表达式.

Freeze-thaw cycle and dry-wet alternation as two typical weathering factors have remarkable influence on soil strength. In order to explore the difference between the influences of the two weathering factors on soil strength and their suction mechanism, a direct shear experiment and matric suction measurement were carried out for the unsaturated remodeled loess with different moistures under condition of both the freeze-thaw cycle and the coupling of freeze-thaw to dry-wet, respectively. The result showed that under freeze-thaw condition, the cohesion would decrease with the number of freeze-thaw cycle in the form of exponential function, the internal friction angle could increase exponentially with the number of freeze-thaw cycle, and the shear strength would increase with the number of freeze-thaw cycle;and under the condition of coupling of freeze-thaw to dry-wet, the cohesion and internal friction angle would exponentially decrease with the number of the coupling of freeze-thaw to dry-wet and the shear strength would decrease with the number of that coupling. The dry-wet path would have a certain influence on the shear strength;the shear strength and strength parameter in the case of wetting first and then drying would be greater than that in drying first and then wetting. A quantitative expression of variation of cohesion and internal friction angle with the number of coupling of freeze-thaw to dry-wet was given out respectively.