Numerical Simulation Of Gravity Erosion Characteristics Of Coarse Sand Bank Slope In Desert Small Watershed Of Upper Yellow River

The desert coarse sand bank slope in the "ten tributaries" watershed gravitycollapsing due to the erosion of rainstorm flood,pouring into the Yellow River in theform of hyper-concentrated flood.It is one of the important sources of coarse sand inthe Ningmeng reach.The sediment disaster seriously affects the stability of theecosystem and the health of the Yellow River.In this paper,the typical tributary"Sudalaer" desert small watershed was selected as the research area,and fieldobservation,laboratory tests and numerical simulation were used as the main researchmethods to explore the mechanical mechanism of gravity erosion and slump processand types of desert coarse sand bank slope,and to make a comparative analysis withloess bank slope slump characteristics.The main research results were as follows:(1)Through field investigation and sampling analysis,three factors including cohesion,internal friction angle and underground water level are selected as the main factors affecting bank slope slump,and sensitivity analysis is carried out by numerical simulation.The results showed that during the transition process from coarse sand to loess in the "ten tributaries" surface material composition in the upper reaches of the Yellow River,the bank slope stability gradually increasing with the increase of soil cohesion and internal friction angle,while decreasing with the increase of underground water level.The stability of bank slope was most sensitive to the change of cohesion,followed by internal friction angle and groundwater level.(2)Based on Abaqus numerical simulation software,the numerical simulation of bank slope collapse process is carried out with the main parameters of cohesion.The results show that cohesion mainly affects the stability of bank slope by controlling the time of plastic deformation and complete instability of bank soil.The greater the cohesion,the longer the plastic deformation and complete instability of the bank soil,the stronger stability of the bank soil.The most dangerous part of bank slope instability is mainly concentrated at the foot of the slope.The lateral erosion of water flow at the foot of the slope has played an important accelerating role in bank slope collapse.(3)GEO5 geotechnical engineering numerical simulation software is used to calibrate the model parameters through laboratory tests such as permeability coefficient determination and particle gradation analysis.The numerical simulation of slump types is respectively carried out on coarse sand and loess bank slope in the study area.The results show that due to the cohesive force coarse sand bank slope is mainly layered and flaky slump,while loess bank slope is lumpy slump.Compared with the curved sliding of loess bank slope,the coarse sand bank slope is broken-line sliding,and the sliding type is vertical.The simulation results are qualitatively consistent with the measured results.The research results have certain scientific significance for the next step of coupling factors such as erosion of slope toe water flow,quantitatively estimating the amount of erosion slump,revealing the mechanism of erosion slump,establishing a mathematical model of sediment yield due to hyper-concentrated flood erosion in line with the real physical picture,and further enriching the theoretical system of soil erosion in arid areas,and have important practical guiding value for guiding the comprehensive management of soil and water conservation in desert basins.