Study On Seepage And Stability Of High Embankment On Expressway Filled By Coarse Grained Soils On Sloping Ground Under Rainfall Conditions

When constructing highways in the hilly areas of the south,it is inevitable that some high-fill embankments will need to be filled due to factors such as topographic conditions.Coarse-grained soil is widely distributed in the mountainous areas of southern China.Therefore,coarse-grained soil is used as a subgrade.Fillers are a common practice.In the case of the southern rainy season,the high embankment slope is likely to be unstable and slippery,especially the embankment on some natural slopes.Therefore,the stability of the coarse embankment high embankment needs to be particularly noticed.Therefore,This paper is based on the National Natural Science Foundation of China,"Research on temporal and spatial evolution and disaster mechanism of transient saturated region of coarse soil high embanklent slope under extreme rainfall conditions(51508042)",and carries out the one-dimensional rainfall infiltration test of coarse-grained soil,establishes the phase calculation model through finite element software,and compares the calculation with the test results,and tlhen combines the test results to develop the seepage characteristics and stability of the high-grain soil slope under different rainfall conditions.The conclusions of the study are as follows:(1)The one-dimensional seepage test model of coarse-grained soil with different particle gradation and different rainfall intensity was carried out by using the one-dimensional seepage test device of coarse-grained soil.The test results show that:The variation law of volumetric water content of each feature point can be summarized as"elevation-stationary-elevation-stationary"and,elevation-reduction-stationary-elevation-stabili ty".The smaller the unevenness coefficient of the coarse-grained soil sample,the larger the initial moisture content of the soil sample,and the greater the water content at saturation,but the smaller the stable water content after the end of drainage.The larger the unevenness coefficient of the coarse-grained soil sample,the larger the initial matrix suction,and the shorter the time when the soil-like matrix suction becomes zero.(2)The corresponding one-dimensional seepage calculation model is established by finite element software,and the one-dimensional seepage test of indoor coarse-grained soil under the same conditions is simulated.The variation of volumetric water content is not much different from that obtained by indoor model test,indicating the indoor interior of this paper.The one-dimensional seepage test results of eoarse-grained soil are reliable.(3)The numerical analysis results of seepage characteristics of coarse embankment high embankment under different rainfall conditions show that:At the beginning of rainfall,the transient saturation zone first appears at the slope of the embankment.As the rainfall time changes,the transient saturation zone gradually expands into the interior of the slope,and the shape of the expansion is ’J’.When the rainfall time is constant,the greater the rainfall intensity,the greater the depth of the influence of rainwater on the pore water pressure change of the slope soil.Under rainfall conditions,the pore water pressure of the coarse-grained soil slope embankment gradually increases from the inside to the outside.As the slope inclination increases,the saturation zone appears at the foot of the slope.(4)The numerical analysis of the stability of coarse embankment slopes under different rainfall conditions shows that:The greater the rainfall intensity,the greater the influence of rainfall on the stability of the coarse embankment high embankment.Under the same rainfall conditions,the larger the dip angle of the bedrock,the smaller the initial slope safety factor of the high-grain soil slope embankment,and the smaller the impact of rainfall on the safety factor of the slope.When the saturated permeability coefficient is greater than the rainfall intensity,the safety factor of the slope decreases uniformly with the rainfall.When the saturated permeability coefficient is less than the rainfall intensity,the amount of rainwater is deep.Not controlled by rainfall intensity,it is difficult to have a substantial impact on slope stability in a short period of time.