Study On Infiltration Law Of Loess Slope Under Different Rainfall Conditions

In China,the area covered by loess is 6.3×105km2.Natural disasters often occur in the loess area.The occurrence of these disasters is often unpredictable and large.Once they occur,they will seriously threaten people's lives and property safety.This has added many difficulties and serious constraints to the construction of the loess area.In order to further understand the internal law of loess landslide disasters,this paper takes loess in Sanmenxia area as the research object.Firstly,the basic loess geotechnical test is carried out to obtain the natural soil parameters.Secondly,the samples close to the natural soil parameters are prepared according to the test parameters,and the indoor raindrop splash test is carried out to analyze the law of single raindrops on the splashing damage of the loess slope.Based on the single raindrop splashing damage test,the variation of slope erosion and stability of rainy rainfall process was further studied.Finally,PLAXIS 2D finite element software was used to analyze the change and saturation of slope matrix suction under four different rainfall intensity types.Degree of change,stability and maximum displacement.The main conclusions of this paper are as follows:(1)Based on the analysis of rainfall characteristics in loess area,this experiment has obtained that the single raindrop splash is divided into three stages,and the 0-30 min soil is subjected to the initial stage of the greatest damage caused by raindrop splashing;the surface layer of the soil reaches saturation at 30 min-50 min.The change of the hole depth is no longer obvious and approaches the stationary mid-term stage;the accumulated water in 50 min-60 min gradually increases with the final stage of the collapse.(2)Based on the analysis of the law of single-rain drip splashing loess soil,the raindrop experiment was carried out,and the tiny potholes of raindrops splashed on the slope surface began to be around 10 min,and as the rainfall lasted,the slope appeared and filled with potholes.With the increase of accumulated water,the slope forms runoff and carries a large amount of loess particles.The duration of rainfall makes the erosion surface appear on the slope surface and gradually expands to both sides and deep,and small-scale collapse occurs on both sides of the channel.And there are many tensile cracks at the trailing edge of the slope.When these cracks extend downward and the cracks are connected to each other,the slope will be in a more dangerous state.When the cracks are connected to each other,the slope will have a small slip.The rainwater penetrates into the crack,the water content inside the slope increases rapidly,the strength of the soil decreases,and the small slump continues,and then the overall slope of the slope is pulled.The maximum volumetric moisture content of the model when the landslide occurred was about 40.9%-43%.(3)Based on physical test parameters and mechanism analysis,PLAXIS finite element software was used to simulate four different rainfall conditions.The uniform rainfall has prolonged with rainfall,and the matric suction and saturation change uniformly,and no sudden change point occurs.The other three types of rainfall types are: the weakened type is at 24 h,the intermediate type is at 48 h,and the enhanced type is at 72 h.The safety factor from the largest to the smallest is enhanced > uniform type > weakened type > intermediate type;the maximum displacement from large to small is intermediate type > weakened type > uniform type > enhanced type,the result shows: the same slope Under four different rainfall intensity types,the intermediate type of rainfall is the most unfavorable state,and the safety and maximum displacement after rainfall are the largest.(4)According to the most unfavorable rainfall intensity type,the rainfall simulation comparison analysis of 30°,45° and 60° slopes shows that the suction and saturation points of the three different slopes are 30° and the slope is at 60 h and 45°.The slope and the 60° slope are at 48 h,and the safety is from 30° to >45° slope>60° slope.The displacement changes from 60° to 45°>30° slope.