Study On Physical Model Test Of Yangpoyao Loess Landslide Induced By Rainfall

Aiming at the problem of landslide geological hazard in loess area,this paper carried out physical model test and numerical simulation analysis,hoping to make beneficial progress in the deformation mechanism and mechanism of loess landslide hazard.The paper is based on the Yangpoyao landslide located in the Huangling-Yan’an Expressway section number LJ-11 in Shaanxi Province,and analyzes the health status of the Yangpoyao landslide during the operation period through data collection,field survey and long-term monitoring data.The models are similar in geometry,and the physical model test of rainfall-induced landslides is designed and carried out.Through multi-means and multi-method monitoring technology,the whole process of disasters such as model deformation development,rainfall infiltration,moisture content change,and destruction process is monitored and studied.The interaction law between deformation failure and rainfall and infiltration,and on this basis,through numerical simulation analysis,reproduce the rainfall-induced landslide model failure process of the physical model test,and compare the results of the numerical analysis with the physical model test results to study the rainfall pattern The disaster characteristics of loess landslides reveal the catastrophe mechanism under the action of rainfall infiltration,and provide theoretical basis for the prevention,prediction and early warning of natural disasters such as slopes and landslides in loess areas.The main research contents and conclusions of this paper are as follows(1)In terms of the mechanical properties of rock masses:the basic physical and mechanical properties of the loess in the Yangpoyao landslide area have been accumulated through preliminary experimental studies;the soil-water characteristic curve test of the loess has been carried out to study the saturated-unsaturated characteristics of the loess,and established Based on the Fredlund-Xing model and the empirical formula of soil-water characteristic curve with dry density as the parameter,the relationship between fitting parameters and dry density is discussed.(2)In terms of physical model test equipment:designed the working principle of the variable angle landslide physical model test box,and drawn the equipment processing and production drawings;based on the historical rainfall statistics of the project area,the artificial rainfall equipment was designed Technical parameters;developed a device that can be used in the physical model test of the loess landslide disaster process.(3)In terms of physical model test system:a physical model test test system that combines traditional sensors with distributed optical fibers,photography and video,and a combination of contact and non-contact is designed to realize the soil pressure,pore water pressure,and A landslide disaster monitoring system that records the whole process of volumetric water content,slope deformation and disasters.(4)In terms of physical model test plan:based on similar principles,the size of the physical model of the landslide was designed;based on the regional rainfall data,the test rainfall type and strength plan was formulated;based on the landslide deformation failure mode,selected Reasonable monitoring sensors are designed and the relative monitoring plan is designed;using layered filling and sensor pre-positioning methods and technologies,a physical model of Yangpoyao landslide meeting similar principles is produced,and related monitoring equipment is installed and debugged;according to the established Test plan and procedures,and orderly carried out the rainfall-induced deformation and failure test of the indoor physical model of Yangpoyao landslide.(5)In terms of physical model test research on the deformation and failure mechanism of loess landslides:the deformation and failure form of loess slopes is shown as shallow sliding failure caused by erosion;during the rainfall process,the change in earth pressure becomes slope foot>slope waist>slope The top;the moisture content is manifested in that the moisture content in the early stage of rainfall infiltration rapidly increases and then tends to be gentle,and the moisture content of the slope foot reaches its peak before the middle and top of the slope.The failure mode can be divided into four stages,namely,rainfall infiltration slope surface saturation runoff-slope foot erosion erosion damage-lower part collapse to form the empty surface-upper slope body sliding and overall failure;this landslide mode occurs in the shallow surface layer with a depth of slope 0～0.2m below the surface.The process of slope erosion can be divided into "cavity erosion-chip erosion-gully erosion",that is,the runoff layer appears after the transient saturated layer is formed on the slope at the beginning of rainfall,which leads to cavitation erosion at the slope angle;as the rainfall continues,the cave erosion develops into slices Formation of shallow and short rills;gully erosion intensified in the middle and late periods of rainfall,developing into deep and lateral erosion.This infiltration and erosion phenomenon is basically consistent with the on-site survey of Yangpoyao landslide.(6)In terms of numerical simulation analysis:Based on saturation-unsaturation theory,ABAQUS finite element software is used to simulate and analyze the rainfall infiltration and deformation evolution process of Yangpoyao slope.Combined with the results of physical model tests,the evolution process of rainfall infiltration,erosion and seepage field in the process of deformation and failure of loess landslides is analyzed,that is,the early rainfall causes the soil to wet,the shallow seepage field changes,and a transient state is formed at the slope toe Saturation zone and transient water pressure;as the rainfall continues to fully saturate the slope and the top of the slope,the soil mass increases in water absorption and the saturation of the shallow soil further increases;the slope surface stability undergoes qualitative changes in the later stage of the rainfall,leading to collapse or slippage,Which promotes the overall failure of the loess landslide,showing a shallow failure mode.Figure[50]Table[10]Ref.[77]...