Mesoscopic Numerical Simulation Of Triaxial Test Of Coarse Grained Soil Based On PFC3D

Mesoscopic mechanical properties is the main research content of mechanicscharacteristics of coarse grained soil. At present, tests and measurement technology can notobtain the mesoscopic mechanics parameters, neither well reveal macro mechanicalproperties inherent mechanism of coarse grained soil. As a kind of discrete element method,PFC is one of the main means of mesoscopic analysis. In PFC triaxial numericalsimulation experiment, establishing efficient and reacting indoor sample particle sizedistribution of the numerical model is the basis of triaxial numerical simulation, selectingthe regulation order and adjusting the degree of the mesoscopic parameters value is the keyto improve the efficiency of triaxial numerical simulation, using different mesoscopicanalysis methods which reveal the coarse grained soil mechanics characteristic internalmechanism is the ultimate goal of triaxial numerical simulation test. Therefore, this articleis based on indoor triaxial test results, carrying out the PFC triaxial numerical experiments,proposing efficient numerical modeling method and a new mesoscopic analysis method,analyzing the influence of the mesoscopic parameters on the macroscopic mechanicalproperties, and the mechanic and deformation sensitivity of the mesoscopic parameters.The main research contents and results are as follows:1) Based on the existing indoor large-scale triaxial test data, the program is compiledin order to establish PFC3D triaxial numerical test model.2) The first time proposing weighted average method to generate particles in themodel, to avoid lower computational efficiency due to a vast number of smaller diameterparticles. Meanwhile, based on the weighted average of particle size can obtain the triaxialnumerical test stress strain curve results perfectly.3) Analyzing shearing process of particle displacement field and particle rotation fromthe perspective of mesoscopic under different confining pressure, and based on theirchanges to analyze the mesoscopic phenomenon of indoor triaxial test nature of the macromechanical properties.4) The first time applying measure model into the three-axis numerical test model,through the measurement model program is compiled, using133measurement spheres totest the fissure distribution inside the sample, according to the change rule of thecoordination number, porosity and volumetric strain within the spheres in the shearingprocess to analyze the spatial distribution of the shear plane in triaxial model, to get the space shear plane of triaxial numerical experiments.5) Carrying out the mesoscopic parameters impact sensitive analysis on strength anddeformation of coarse grained soil, these mesoscopic parameters include that porosity,particle coordination number, the ratio of normal stiffness and the tangential stiffness(kn/ks), particle size distribution, shear velocity rate and friction coefficient. It is concludedthat the sequence of mesoscopic parameters sensitive influence on the peak strength ofcoarse grained soil is: kn/ks> friction coefficient particle size distribution> shear velocityrate> porosity> coordination number.