CALIBRATION METHOD OF MICROSCOPIC PARAMETERS FOR SIMILAR MATERIAL OF SURROUNDING ROCK BASED ON DEM

Abstract

Similar materials of surrounding rock are used to simulate the rock mass in the geomechanical model test. The discrete element method has the advantage of simulating the behavior of fractures between particles at the micro-scale, which can further reveal the failure mechanism of surrounding rock in combination with the model test. However, microparameters need to be calibrated before the simulation. In this paper, three kinds of bond models are described, and their application is analyzed. The soft-bond model is determined as the constitutive model of particles' contacts. Then, the simulation method of the biaxial test is introduced in detail, and the simulation results of the rigid-wall and flexible-wall methods are compared. Furthermore, based on the control variable method, a large number of biaxial tests are carried out by the rigid-wall method. Through single-factor sensitivity analysis and multi-factor variance analysis, the qualitative relationship between macro- and micro-parameters and the significant influencing factors of each macro-parameter are obtained. On this basis, the multivariate nonlinear multi-scale mathematical model is established by regression analysis. The appropriate micro-parameters are obtained by solving the proposed mathematical model using three optimization methods combined with the results of laboratory test measurements. This entire process constitutes the calibration method proposed in this paper. The reliability of the calibration method in this paper is verified by comparing the calculated macro-parameters, stress-strain curves, and failure modes with those of laboratory tests.