Study On Water Movement Law In Loess Slope Under The Geological Structure

Loess is widely distributed in China.The metastable structures make their special accumulation conditions,which constructs the special geologic feature.Geologic hazards such as collapse,landslide and loess collapse are easy to be triggered by precipitation.This article takes the loess slope in Southern Jingyang Plateau of Shaanxi Province as the research object.The two-dimensional variable saturated seepage models of vertical profile of loess slope and the saturated-unsaturated model under different geological structures were established based on field survey,available data and saturated-unsaturated seepage theory to explore the influence of the existence of fissure and paleosol on the water migration law in the loess slope of Jingyang South Plateau.The main conclusion is as follows:1.The rainfall infiltration water can seep into the slope rapidly through the fissure first,which is easy to enrich around the fissure and the soil moisture content rises as well.After the rainfall stops,the water accumulated in the fissure dissipates to the surrounding,and the water near the fissure dissipates much faster than that in other areas.The influence range in the fissure top is smaller than the bottom,and the horizontal direction is smaller than the vertical.The deeper the fissure develops,the greater the influence range,and the faster the water dissipates,leading to the further expansion of the fissure.When the permeability coefficient in the slope is different,the greater the permeability coefficient,the greater the influence range of the fissure as well as the faster the water dissipation around the fissure.2.It is concluded that the distribution of water content of slope soil changes regularly with the increase of depth.When there is paleosol in the slope,the water content is hindered by the paleosol during the infiltration process,and the rate of downward dissipation is slowed down,which is easy to accumulate above the paleosol layer.The moisture content above the paleosol layer is much larger than that below,and the water content distribution in the slope shows obvious horizontal stratification phenomenon.When there is no paleosol in the slope,there is no obvious horizontal stratification in the distribution of water content in the slope.After the rain stops,no matter whether there is ancient soil in the slope,the water dissipation rate in the slope is slow.3.When the fissure do not run through the paleosol,the water will accumulate above the paleosol for a period of time,and the moisture content above the paleosol layer will increase.When the fissure run through the paleosol,the water accumulation above the paleosol can reach the bottom quickly through the fissure,making the moisture content under the paleosol rise rapidly and becoming more conducive to the migration of water to the deep soil.The smaller the permeability coefficient of paleosol layer,the more obvious the blocking effect is,and the water dissipation rate in the fissure is slower in the paleosol.The larger the permeability of loess,the faster the water dissipation,and the wider the influence range of fissure in the slope.Comprehensive comparison shows that after the fissure run through the ancient soil,the water accumulation time around the fissure is longer,which will accelerate the fissure expansion and further cause slope instability.