Analysis Of Seepage And Stability Of Expansive Soil Slope With Variable Ratio Under Wetting And Drying Cycles

Expansive soil is a kind of high plastic clay of swell-shrinking. It has a lot of bad engineering properties, such as overconsolidation, multiple cracks, etc. Expansive soil slope is vulnerable to the effects of climate change. A large number of expansive soil slope failure occurred during the period of rainfall or after rainfall. The management of expansive soil slope is difficult. In the process of rainfall-evaporation, for the water sensitive and low permeability of expansive soil slope is concerned, the density of expansive soil and structure change in the local scope. The change of the distribution of volume water content can be reflected directly and it’s also the most direct parameters as the strength of expansive soil.In this paper, through the method of combining indoor test, the theoretical analysis and numerical simulation, the soil column model and different ratio slopes are estabilshed, in order to explore the internal volume water content distribution under the influence of drying-wetting cycles.(1) In the evaporation stage, moisture that in the surface soil dissipates faster. With the soil depth increasing, the water dissipates slower, and presenting some regularity. In rainfall stage, different rainfall intensity affects soil volume water content distribution inside the column is different. Therefore, within a certain range, the greater the rainfall intensity, the more obvious the influence. And over a certain range, increasing the rainfall intensity, its influence is limited.(2) In the sensitivity of the evaporation effect analysis, mainly considering the influence of climate conditions on the evaporation. The results show that the net radiation,wind speed and maximum relative temperature has obvious influence on the soil evaporation, especially the net radiation and the maximum relative temperature is most significant.(3) Under the condition of rainfall and evaporation drying-wetting cycles, the drying-wetting effects have different influence in different parts of the expansive soil slope.The top of the slope is most obvious, followed by the mid and the toe.The curve equation of nzwwwe-D+=max0qqq can well describe the water space distribution characteristics and the rule of the expansive soil slope. On the basis of rainfall evaporation conditions, a relation was put forward to the strength of expansive soil slope with a variable soil depth formula,namely, the relation of strength~volume water content~soil depth.(4) Through the variable slope ratio expansive soil of different gradient seepage analysis, the results show that the slope ratio is different, the influence of rainfall on the slope of the whole seepage field is different. The difference brought by the variable slope ratio are obvious in the early rainfall time or late time. The smaller the slope ratio, thebigger the moisture gradient distribution, and has significant rainfall lagging effect.(5) According to the relation of strength~volume water content~soil depth, the intensity of expansive soil slope was layered. In the view of safety factor, the layered slope is higher than the unlayered slope. Slope stability is affected by slope ratio, just not the slope more slow, the slope safer. For a particular climate and localized parameters, there is a critical slope ratio. When slope ratio is less than the critical slope ratio, the safety factor rises with the slope ratio increasing. When slope ratio is greater than the critical slope ratio,the safety factor decreases with the slope ratio increasing.