Research On Influencing Factors Of Void Ratio And Permeable Coefficient By Using PFC3D Discrete Element Analysis

The void ratio is an important physical parameter that distinguishes discrete porous soils as engineering materials and continuous materials,and it promotes the development of soil mechanics as an independent branch of mechanics.The permeability coefficient it controls is directly related to the soil infiltration stability of major urban projects and infrastructure such as dams and weirs,high soil slopes,underground pipe tunnels,and deep foundation pits.In recent years,accidents and disasters such as slippery slopes,dam failures of flowing soil,tunnel piping,and foundation pit water penetration have occurred frequently,which have become important issues that scholars and the public pay attention to.However,it is very difficult to study the influencing factors of void ratio and permeability coefficient by physical experiments due to comprehensive constraints such as wide distribution of soil particle groups,complex particle morphology,and structure size effect.Through the discrete element method,soil samples with arbitrary particle shape and particle composition can be generated,and parameters such as soil particle arrangement,particle shape,and gradation characteristics can be controlled to realize in-depth soil properties research.Therefore,the research on the influencing factors of void ratio and permeability coefficient based on 3D discrete elements has important scientific significance and practical value for the development of soil mechanics and the design and construction of geotechnical engineering.In this paper,the PFC3D discrete element numerical software is used to verify the accuracy of PFC3D void ratio simulation and measurement.The maximum and minimum void ratio model and the coarse-grained soil permeability model are established respectively,and it is revealed that parameters such as particle gradation and morphology have a significant impact on the void ratio and permeability coefficient.The main work and innovation achievements are as follows:1.The theoretical model of regular arrangement and random distribution of different particles are established by PFC3D software,which verify the rationality of PFC3D void ratio simulation.Combined with the friction coefficient method and the gravity stacking method,a soil modeling method for the maximum and minimum void ratio is established,and the applicability of the particle cluster modeling method for controlling the gradation and void ratio is proved through the comparison of experimental measurements.2.Through the control variable method,soil modeling and void ratio measurement of different particle gradations and particle shapes are carried out.The law that e_{ma x}\e_min of coarse-grained soil are affected by parameters such as particle gradation and shape is revealed,the functional relationship betweene_{ma x}\e_min and parameters such as particle composition and particle shape is established,and the essential reason of the change of soil void ratio is revealed from a micro perspective.3.Based on the CFD-DEM method,the permeability model of coarse-grained soil is established,and the influence laws of void ratio,inhomogeneous coefficient,curvature coefficient,effective particle size,etc.on the permeability of coarse-grained soil are revealed,and the key control factors are given.The water pressure and water flow cloud map of the established permeability model effectively reflect the law of soil seepage and provid a reference for the establishment of the soil discrete element permeability model.