Influence of Microscopic Parameters of Particle Flow Code on Uniaxial Compressive Simulation of Rock/coal Material
Authors: Zhang Jinwang , Cheng Dongliang , Yang Yinchao 
Published: October 2022

ABSTRACT:
Coal and rock materials are naturally formed non-continuous heterogeneous materials. Laboratory tests through field sampling can intuitively and effectively obtain various parameter data of material deformation and failure, thus providing theoretical and data basis for specific engineering design. But the laboratory test cost is high, the labor intensity is big, mainly cannot carry on the repetitive test to the single material, and the numerical simulation calculation just makes up for these shortcomings and can verify the laboratory test results. As a powerful discrete element particle flow analysis software, PFC can truly simulate the microscopic parameters of materials and calculate the deformation and failure of materials. The determination of microscopic parameters of materials has become the primary problem to be solved. At present, only macro parameters of the sample are generally considered in most numerical simulation tests, and the accuracy of the micro parameters is difficult to ensure, resulting in low accuracy of the test results. In order to study the influence of micro parameters on the deformation and failure of specimens in uniaxial compression test, PFC2D was used to establish parallel bond models with different micro parameters (tensile strength, cohesion and bond gap). The uniaxial compression test of coal and rock samples was carried out, and the influence of different parameters on the deformation and uniaxial compressive strength of samples was analyzed. This paper mainly studies the influence of the microscopic parameters of the parallel bond model on the uniaxial compression test results. The research results provide theoretical and data basis for the setting of microscopic parameters in the uniaxial compression numerical simulation test of related materials, and help to improve the accuracy of the uniaxial compression numerical simulation test.

1. INTRODUCTION
In the study of engineering problems related to geotechnical engineering, the research and analysis of rock mechanical properties is the most basic and primary work, which is of indispensable significance to engineering design. In recent years, the particle flow code (PFC) has obtained a lot of attempts and applications in various engineering and rock mechanics studies, which can easily deal with the mechanical problems of discontinuous media, intuitively reflect the fracture development and failure process in the simulated medium, and is widely recognized by the industry. However, the model parameters need to be calibrated in PFC simulation. At present, the "trial-and-error method" is generally used in the calibration of parameters, that is, to find reasonable parameters that are basically consistent with the physical experiment phenomenon through multiple attempts to modify relevant parameters. Due to the lack of effective theoretical guidance, a large number of model calculations have to be carried out to calibrate the parameters. Most engineering models have large volume and slow calculation speed, resulting in low efficiency of parameter calibration. Therefore, the quantitative analysis of the influence of the microscopic parameters of the model on the simulation results and the attempt to put forward the reasonable interval of the microscopic parameters according to the physical test results have important reference significance for the numerical simulation of mechanical tests and related engineering problems.