Analysis Of Rainwater Infiltration In Loess And Slope Stability Under Continuous Rainfall Condition

The infiltration of water in soil is an important factor of landslide in process of the continuous rainfall.At present,there is a lot of research in this area,but there are few studies on the infiltration of rainwater in loess soil,movement law of its moistening front,and slope stability under continuous rainfall with no accumulated precipitation on the ground.The purpose of this paper is to solve two problems,namely,the infiltration law of rainwater under the condition of continuous rainfall without precipitation and the stability of loess slope under the condition of continuous low-intensity rainfall.A series of indoor and outdoor test were carried out.Slope stability is analyzed by numerical simulation,understanding of the law of loess landslide caused by rainfall is deepened.The main research contents are as follows:?1?The author designed and produced a set of simulation process system that can simulate vertical loess soil column under condition of continuous rainfall without accumulated rainfall on surface of the column.Three groups of unsaturated loess tests were conducted under continuous rainfall with no accumulated precipitation on the loess column.The relationship between soil volume moisture contents at corresponding depth monitoring points and rainfall duration was measured.Determined the relationship between vertical seepage stability depth of soil column with different dry density and rainfall time,as well as the relationship between depth of moistening front and rainfall duration.Based on the hypothesis of Green-Ampt infiltration model,a seepage mode of rainfall movement in loess soil under continuous rainfall with no accumulated precipitation in loess area was established,and the hypothesis and seepage mode was verified by the test results.The movement relationship of rainfall infiltration moistening front'depth and seepage stability area'depth in loess area under continuous rainfall with no accumulated precipitation was also further revealed.The result shows that the hypothesis parameter m of seepage moistening front'shape movement of soil column is close to 3 under the condition of the test.?2?A set of outdoor test device for simulating continuous rainfall was designed and made,and rainfall intensity is adjustable within a certain range.The outdoor test loess slope landslide caused by continuous low-intensity rainfall was carried out.Under condition of continuous and uniform low-intensity rainfall,when simulated rainfall test time reached 308.8h from beginning,the 3-meter-high loess test slope occurred a landslide.The landslide area,collapse area and the sliding line of central section were drawn on a diagram,moisture content of the loess test slope at different depths before and after the simulated rainfall test was measured.After the test,undisturbed samples were taken at different depths of the slope,and the slope loess parameters were obtained through laboratory tests.We found cracks on the slope surface and along the top will accelerate the diffusion of water field.When the slope was unstable,there were many cracks along top of the slope and many unstable surfaces were found.?3?Use FLAC^3D software to simulate the stability of slope.Simulation results show that if the parameters are the same,stability coefficient of slope in three-dimensional simulation is greater than that of slope in two-dimensional simulation,the maximum displacement of slope in 3d simulation is less than 2d simulation result.Comparison of simulation and test results show that the displacement and sliding line on the central section are in good agreement with 3d simulation results of the slope.During the simulation,cracks were loaded into the simulating model,and the relationship between depth of crack development and slope safety factor was obtained.When the depth of crack developing along the slope test sliding surface reached 140cm,the slope safety factor decreased from1.92 to 1.03.The influence of crack's developing direction on slope stability was analyzed,as well as influence of crack's quantity.