Discrete Element Triaxial Simulation Of Frozen Sand And Analysis Of The Effect Of Mesoparameters On Macro-meso Characteristics

Frozen soil is an inhomogeneous multiphase aggregate composed of soil aggregates,ice,unfrozen water,and gas,and is a special kind of bulk material;the complexity of the mesoscopic structure of the soil determines the complex engineering of the soil The mechanical properties,and the existence of ice in frozen soil deepens its mechanical complexity;and the past frozen soil mechanical models are mostly established using the theory of continuous media,which regards granular materials as continuous media and ignores the dispersion of frozen soil characteristic.At the same time,although many test instruments and methods have been used to study the static characteristics of frozen soil in the laboratory test of frozen soil,it is difficult to accurately control the boundary conditions and loading methods of the laboratory test of frozen soil.Has greater dispersion.In view of this,on the basis of fully considering the discrete characteristics of frozen soil,this paper uses the discrete element PFC2D numerical model to simulate the static triaxial compression test of artificially frozen sand.Based on the meso-contact bonding constitutive model,it simulates different temperatures and confining pressures.Indoor static triaxial compression test of artificially frozen sand,to study its macro static characteristics(stress-strain relationship),and then study the mesoscopic contact characteristics of soil particles(contact stiffness ratio,friction coefficient,normal bonding force,tangential bonding force))The influence law and meso damage mechanism of the macro static characteristics and meso static characteristics(contact force chain,crack propagation,particle displacement and energy evolution)of artificially frozen sand.The main results are as follows:(1)Taking artificially frozen sand as the research object,based on the meso-contact bonding model,a numerical model of the static triaxial compression test of the frozen soil particle flow laboratory was established,and the frozen soil numerical samples under different temperature fields and confining pressure fields were simulated In the process of indoor triaxial compression,the effect of different temperatures and confining pressures on the macrostatic characteristics of artificially frozen sand was studied.(2)By studying the contact force chain evolution law,crack propagation law,particle displacement law and energy evolution law of frozen soil during loading,the mesoscopic change mechanism of frozen soil is further studied.(3)After the numerical model of the static triaxial compression test of the artificially frozen sand particle flow chamber is established,the meso-contact parameters of different soil particles(normal normal stiffness kn,tangential stiffness ks,friction)The coefficientμ,the normal bonding force n_bond at the contact and the tangential bonding force s_bond)affect the macro and mesostatic characteristics of frozen soil.