Calibration of Microscopic Penalty Parameters in the Combined Finite-Discrete-Element Method

With unique advantages in simulating solid fracture, the combined finite-discrete-element method has become increasingly popular in the rock mechanics field. Nevertheless, a large number of microscopic parameters in the method need to be specified and many of them cannot be directly measured via laboratory tests. Therefore, these parameters must be determined via a calibration procedure. To calibrate appropriate microscopic parameters, we should find the relationship between them and the macroscopic mechanical response. In these microscopic parameters, the normal and tangential penalty parameters play a very important role. Thus, in this paper we study the effect of penalty parameters on macroscopic mechanical parameters in the combined finite-discrete-element method. It is found that as the penalty parameters increase, the elastic modulus and Poisson's ratio gradually approach the experimental values. However, the further increase of penalty parameters has little effect on the elastic modulus and Poisson's ratio when they reach 100 times the elastic modulus. Based on this conclusion, a simple method for the calibration of penalty parameters is proposed, which can be used to quickly determine the penalty parameters according to the uniaxial compression test.