Study On Characteristics Of Runoff And Sand Yield On Loess Slope And Stability Of Slope

The soil erosion in the loess area leads to the deterioration of the ecological environment,exacerbates the instability of the slopes of the loess high plateau,the ditches continue to advance,and the plateau surface shrinks year by year,often threatening people's lives and property safety.The instability of the loess slope caused by rainfall,especially heavy rain,is one of the main factors causing soil erosion.The groundwater level in the loess area is generally higher than that of the riverside.The most important source of groundwater comes from rainfall.The surface water infiltrated into the loess slope after the rainfall,which increased the weight of the slope body,at the same time,the pore water pressure also increased due to the infiltration of rainwater;in the process of turning part of the surface water of the loess slope body into groundwater,the slope The shear strength decreases accordingly;at the same time,the loess is easy to crack under the action of dry and wet cycles,resulting in a large number of joint cracks.Through in situ test of artificial rainfall simulation runoff plot on the ditch head slope,water samples were collected in different periods during the rainfall process,the slope erosion characteristics and rainfall infiltration rules were analyzed;borrow the observed steep slope data to rain on the loess steep wall Scour failure,study the evolution process and mechanism of steep slopes on both sides of the Loess Gully during rainfall collapse;at the same time,the stability of the slope of the trench side taking into account the matrix suction is considered through ABAQUS numerical simulation to clarify the relationship between slope rainwater infiltration with slope and rainfall and rain,Reveal the mechanism of runoff,discuss slope instability,clarify the relationship between slope instability and factors such as rainfall intensity and slope,and provide theoretical support and scientific basis for slope protection.The main research contents obtained are:1.The in situ artificial slope rainfall test was carried out in the field,combining four natural factors: soil factor,rainfall and rain type,vegetation coverage conditions and slope,the soil was set up in Malan loess and Lishi loess respectively,and the rainfall and rain type was divided into 3 hours and a short duration Rainfall and 24-hour long-duration rainfall.The slopes are covered with vegetation and bare slopes,as well as different slope ratios of 5 °,15 ° and 30 °.The characteristics of runoff and sediment production on the slopes of loess natural slopes are analyzed for the prevention and control of soil erosion.And provide theoretical basis for ecological restoration research.2.Field investigations were conducted on the damage of the trench slopes in the loess area around Qingyang.At the same time,in order to study the evolution process and mechanism of the collapse of the steep walls on both sides of the loess ditch during rainfall,on the side of a rectangular foundation pit 4m long,1m wide and 1.7m deep The vertical slope is directly washed away by rain.Under the condition of rainfall intensity of 1mm / min,a longperiod slope erosion test was carried out on the vertical slope of the long-side foundation pit.3.Under the theory of rock-saturated saturated-unsaturated seepage,considering the effect of rainfall infiltration,the finite element software numerical simulation is used to analyze the rainfall infiltration law and stability of the loess slope under different rainfall types and slope conditions.Based on the limit equilibrium theory,the slope stability coefficients under different working conditions are obtained.At the same time,the numerical simulation results prove that the infiltration depth of heavy rainfall generally does not exceed 4m.