The Erosion Damage Characteristics And Numerical Simulation Of Loess Slope

Loess is widely distributed in China, the problem of rainfall damage of loess slope hasbeen concerned by engineering and academia. Current researches are mainly on the issue forthe overall destruction of slope, and more concentrated in the northwestern region. Theresearches are relatively few in northeast of China,especially in the region of loess of westernLiao Ning province. Based on the summarising and further studing on the engineeringgeologic characteristics of loess region of western Liao Ning province, doing the simulatedrainfall model slope erosion experiment, using the ABAQUS finite element software, using thePFC3Dparticle flow software, and Cellular Automaton modeling theory establishedmathematical models. Doing three perspectives numerical simulation of indoor simulation test,doing comparative analysis to data of indoor simulation test. Studied the evolution process ofslope erosion by rainfall and erosion mechanism. Especially on the cause and development ofrill erosion, making the fruther studies on flow and sediment transport of soil erosionprocesses, doing detailed description of erosion process. Provides a theoretical basis forestablishing loess erosion prediction model of western Liao Ning province. Main content asfollows:1. Summarising and studing further on the engineering geologic characteristics of loessregion of western Liao Ning province. Clarifies the cause characteristics of loess, materialcomposition, physical and mechanical properties and its microstructure characteritics.Obtained the stress-strain relationship of different loads and different moisture content.Studied microstructure the changing law before and post collapse of loess. Revealed themechanism of loess collapsibility from pore number and fractal characteristics: silt is the asthe main content, and different granulometric composition with loess of northwest China.Learn the range of variation of the natural density, dry density, natural moisture content, voidratio, c, values.2. Design the indoor rainfall simulation model system for slope erosion, and finished therainfall model slope erosion experiment in three different rainfall intensities and five differentslope gradients. Draw the conclusion that the critical slope of rainfall erosion is in the range of36.5°~44°in Liaoxi area. Do real-time monitoring on slope surface water infiltration, particle movement on slope and the change of slope shape. Get the result that changing law ofmoisture close to slope surface. Summarize that the slope surface erosion process consists ofsheet erosion-rill erosion-gully erosion, characteristics and evolution of each stage.3. Doing numerical simulation of simulated rainfall model slope erosion experiment withABAQUS finite element program. Analysis the evolution law of rainfall intiltration and slopedeformation in different rainfall intenstity and slope gradient conditions using water-soilmechanics coupling mechanism. In one slope condition, the duration of rainfall on slopesurface has more affected on the degree saturation of soil. The flow speed direction near theslope surface has the opposite direction to the slope normal, except the top slope and footslope that the reason is boundary conditions restrictions and different direction of rainfall.Different rainfall intensity has much influence on energy of slope runoff. Increasing of rainfallintensity is made of Rainfall and raindrop speed. The result is that the energy and velocityincreasing of runoff has influence on the degree of erosion damage. On same slope and rainfallintensity, pore pressure velocity has increased as the rainfall continued. As the matric suctiondecreased, shear strength of soil has reduced. So the stability decreased.4. A series of experiments of slope rainfall erosion were done in laboratory for steep loessslope with70°under a rainfall intensity of2.7mm/min. According to the experiments it wasfound that as the rainfall lasting the energy and erosion intensity of water flow increased. Theerosion pattern was then changed from splash and sheet erosion to rill erosion and finallyevolved into gully erosion and collapse on top of the slope. Based on the experiment,simulated the slope erosion process with PFC3Dwith fluid-soil coupling method, observed thelarge deformation of particles, simultaneously obtained microcosmic parameters such asparticle motion trace, porosity, water flow rate in fluid cells, from their quantitative changeprocess got the distribution of degree of erosion and erosion intensity of water flow in slope, itindicated that the degree of erosion and the erosion intensity of water flow on top of the slopewere strongest and both reduced as the height decrease, which was consistent to the indoormodel experiment.5. According to the mathematical theory of cellular automata, establishing CA slopeerosion damage simulation model. Simulated the erosion damage process of different rainfallintensity. Obtained the digital data of rill erosion in different time. Statistic the rill number,rillintensity and rill total length of different rainfall intensity. Obtained rill evolution rates ofdifferent rainfall intensity and surface roughness. Found that erosion stoped at step500. Rill morphology and density tends to be stable.