基于温度路径的冻融作用下黄土强度及微观结构研究

Study on the strength and microstructure of loess under freeze-thaw based on temperature path

在季节性冻土区,冻融作用诱发黄土滑坡的本质是冻融循环作用下黄土物理力学性质的劣化,探明冻融作用下温度以及水分迁移对黄土强度的影响及其机制是必要的。以山西省柳林县某黄土边坡为例,采用一种新的冻融循环方式即按照土体每年历经的温度路径进行冻融循环,研究在温度动态变化的冻融循环作用下土体的抗剪强度变化规律以及反复冻融循环作用对土体黏聚力、内摩擦角和微观结构的影响。结果表明:在一轮冻融循环过程中,土体强度与温度呈负相关关系,低温对土体强度影响较大。随着冻融次数的增加,土体黏聚力呈指数函数下降,内摩擦角几乎没有明显变化。微观试验表明,随着冻融次数的增加,土体内大颗粒破碎化,孔隙增多,表现为颗粒趋于均一化,中等大小(5~10μm)孔隙占比最大。本次研究模拟了土体经历的温度变化过程,为该地区季节性冻融型黄土滑坡防治提供了借鉴作用。

In seasonal frozen soil regions,the essence of loess landslides induced by freeze-thaw cycles is the deterioration of the physical and mechanical properties of loess.It is necessary to find out the influence of temperature and water migration on the strength of loess under freeze-thaw cycles and its mechanism.Therefore,a new freeze-thaw cycle method is adopted,which is carried out based on the temperature path that the soil goes through each year,to study the law of the shear strength of the soil under the action of the freeze-thaw cycle with dynamic temperature changes and the influence of repeated freeze-thaw cycles on soil cohesion,internal friction angle and microstructure.The test results show that during a freeze-thaw cycle,the soil strength is negatively correlated with temperature,and low temperature has a greater impact on the soil strength.As the freeze-thaw cycles increase,the cohesion of the soil decreases exponentially,and the internal friction angle has little change.The microscopic test shows that with the increase of freeze-thaw cycles,the large particles in the soil are broken and the pores increase,indicating that the particles tend to be uniform,and the medium-sized(5-10 μm)pores account for the largest proportion.This study simulates the temperature change process of soil,providing a reference for the prevention and control of seasonal freeze-thaw loess landslides in this area.