Study On Rainfall Erosion Damage Characteristics And Mechanism Of Loess Landfill Slopes

Lanzhou City,located in Gansu Province,is a typical mountain valley city characterized by rolling hills and gullies on both sides of the north and south.The area experiences high rainfall and frequent geological disasters such as landslides,slides,and mudslides.With the development and construction of the main city and the intensification of human engineering activities,a large amount of abandoned slag(mainly loess)has been used to form the side slopes of the landfill loess,posing a huge potential threat to the occurrence of mudslides in the main city.To address this issue,this paper focuses on the scientific problem of rainfall erosion on the landfill loess slope,starting from the perspective of material recharge of loess mudflow.Through field research,model tests,and numerical simulations,we studied the erosion and damage characteristics of the landfill loess slope under rainfall conditions and revealed its erosion development mechanism.Our main findings are as follows:(1)We obtained an overview of the study area and made a new definition of the physical and mechanical properties and microscopic pore structure characteristics of the landfill loess.The fill loess has a high content of fine particles and high saturated hydraulic conductivity,and the average pore fractional dimension of the fill loess is1.251,the large and medium shelf pores collapse into more stable small shelf pores,and the pore fractional dimension number decreases linearly with the increase of water content.(2)Based on indoor rainfall scour erosion tests with different slope degrees and different slope cutting degrees,we analyzed the development characteristics of scour erosion and the response change law of soil and water parameters of landfill loess.We found that the erosion of the slope surface increases with the increase of slope degree,and the erosion damage site gradually shifts from the bottom to the top of the slope.(3)Using finite element analysis software ABAQUS,we established a threedimensional model of scouring and erosion on the slope of landfill loess and analyzed the changes of soil and water parameters of the landfill body under different working conditions.We found that the foot of the slope is most easily damaged under the action of rainfall scouring,and the horizontal displacement of the slope is linearly increasing with the slope.(4)We analyzed the mechanism of slope erosion by slope erosion using the principle of soil and water dynamics.We found that in the sheet erosion stage,the critical runoff velocity required to start the surface soil particles on the slope is positively correlated with the slope gradient.In the gully cutting erosion stage,the larger the slope gradient,the smaller the critical rupture angle required for destabilization damage to occur in the gully cutting slope.(5)Based on soil erosion theory,we analyzed the influence of different slope gradients and cut slopes on the erosion and sand production of landfill loess slopes.We found that the critical slope of the landfill loess slope is around 41° and that erosion sand production decreases with the increase of slope cutting degree as a power function.Our research provides valuable insights for the prevention and control of geological disasters and comprehensive management of soil erosion in Lanzhou City.