Research On Discrete Element Simulation Of Unsaturated Rainfall Infiltration On Slopes And Update Of Numerical Model

Rainfall infiltration is a key factor affecting the safe and stable operation of slopes.In order to systematically and efficiently study the stability of slopes under rainfall conditions,engineering geological exploration,mechanical tests,physical model tests,numerical simulation technology,machine vision technology,automated processing technology,and theoretical analysis are combined with the Nanping road slope as the research background.A discrete element unsaturated infiltration model is established,the stability of Nanping road slope under extreme weather rainfall is predicted,and the updating process of numerical model is realized.The main study components and findings are as follows:(1)The engineering geology,regional topography,climate and hydrology and the factors affecting slope failure in the study area are systematically investigated,and the parameters are measured by indoor physical and mechanical tests.The slope soil type is loose sand,and the surface cracks are numerous.The slippery area is located in the upper part of the slope,and the deformation area is mainly concentrated in the middle of the slope.In the case of rainfall,the slope is prone to collapse,softening,prone to landslides.(2)According to the topographic terrain characteristics of road slopes,a road slope multi-field information monitoring system is established.Sensor equipment and trinocular vision equipment are installed at dangerous points with landslide hazards.The monitoring equipment realized all-day operation and uploaded the data in real time.Through the on-site monitoring data,it is determined that this slope is a rainfall-induced slope,and the monitoring data of retaining wall force,seepage pressure and water content sensor changes with the rainfall data.(3)A novel rainfall infiltration model is developed using discrete element software(PFC3D)by integrating water diffusion,strength attenuation and seepage force.The model is applied to a road slope in Nanping City,Fujian Province for rainfall infiltration analysis.The water content distribution law,the function relationship between shear strength and water content and the calculation results of infiltration rate in different periods are obtained.The validity of the model is verified by comparing the simulation results of water content with the field monitoring data.In order to obtain the accuracy of the model application,it is compared with two empirical infiltration models,and the comparison results of the three models show that the simulation results of this model are in good agreement with the monitoring data.(4)To verify the effectiveness of the newly developed rainfall infiltration model for slope stability analysis,this paper uses numerical simulations to invert three rainfall events.The results are validated using 3D reconstruction techniques.The slope stability of January 22-23,2022 is illustrated in detail.The results show that the top of the trailing edge is the first to deform after the rainfall infiltration occurs,and the deformation trend gradually moves downward.The three-dimensional reconstruction results show that it is basically consistent with the numerical simulation results.(5)The validated rainfall infiltration model is used to predict the stability of road slopes in Nanping under extreme rainfall.The rainfall prediction is implemented for the slope based on the rainfall intensity of a fifty-year event,a hundred-year event and a thousand-year event.The results show that the slope soil is seriously affected by seepage during extreme weather rainfall.Water content increases violently,shear strength damage is obvious and soil loosening occurs.The slope will collapse in a large area,and the greater the intensity of rainfall,the greater the scope of slope collapse.(6)A technique for numerical model updating is proposed using Python,CloudCompare and PFC software.It uses the surface update method for the geometry update.The update of hydrological and material parameters is performed using the function fitting method.The automated trimming of the numerical model is implemented using Python.The updated results of the numerical model are compared with those obtained by following the initial numerical model in combination with the indoor physical model.The monitoring data is used as the basis,and the slope collapse effect in the field is used as the reference.The results show that the updated results of the numerical model are in good agreement with the field monitoring results.