Research On Numerical Simulation Of Triaxial Tests On Gravelly Soil Based On Dem Of Irregularly Shaped Particles

The mechanical properties of core gravelly soil directly affect the settlement deformation and structure safety of earth-rock dam core wall.The gravelly soil of core wall,as a kind of soil-rock mixture,is a complex multiphase mixed medium composed of a certain grade of broken stone and cohesive soil.And it is characterized by heterogeneity and discontinuity.At present,it is difficult to study the mechanical properties of gravelly soil from a mesoscopic perspective through in-situ test and laboratory test.However,the numerical simulation method can well reveal the intrinsic mechanism of deformation and failure of gravelly soil.The discrete element numerical analysis method aiming at solving the problem of heterogeneity and discontinuity can study the motion forms of particle rotation,slip and separation generated by the interaction of gravel and soil in gravelly soil.However,the existing numerical simulation studies on gravel soil focus on the proportion of gravel blending and the spatial distribution of gravel,and lack of consideration of the influence of irregular gravel particle shape factors on the mechanical properties of gravelly soil.Therefore,a three-axis numerical simulation method based on discrete elements of irregular soil in gravelly soil is proposed.The following main research results have been achieved:(1)In view of the lack of consideration of the influence of irregular gravel particle shape factors on the mechanical properties of gravelly soil,an irregular threedimensional form gravel model library is constructed based on 3D laser scanning technology and a three-variable shape evaluation standard is proposed to classify the particle shape characteristics.The results show that the core wall gravel formed by the blasting is distinct and has different shapes and the proposed three-variable shape evaluation standard is simple and effective,and can accurately identify the multiple shape characteristics of irregular gravel.(2)A particle flow modeling method based on particle in-situ replacement is proposed,and the particle flow model is verified by a certain experimental data from Southwest.By loading the constructed standard sphere model and the irregular particle model separately,the simulation results show that the particle in-situ replacement method can effectively avoid the deviation of test results caused by the randomness of gravel distribution of different samples.And the PFC modeling method based on particle in-situ replacement method is reasonable and can be used for subsequent influencing factors analysis.(3)Based on the above shape research and modeling methods and taking a largescale hydropower project in Southwest China as an example,a series of triaxial compression numerical tests with different influencing factors are carried out to explore the effects of particle shape,stone content,mesoscopic distribution,loading speed and PFC mesoscopic parameters on the mechanical properties of gravel soil under irregular particle morphology.Numerical simulation results show that the shape of the gravel has a significant influence on the macroscopic mechanical properties of the gravel soil.Influence of gravel shape on shear strength of gravelly soil has regular changes and the uniformity of the number of different types of gravel helps to increase the strength of the sample.Stone content,mesoscopic distribution,model loading speed and PFC mesoscopic parameters have different effects on various mechanical properties of gravel soil and the complexity and crossover between different influencing factors caused the dispersion of the macroscopic mechanical properties of gravelly soil.