A comprehensive parametric study of grain-based models for rock failure process simulation

Abstract

Grain and contact are the two key components in 3DEC-GBMs (grain-based models) because they control the micro-mechanical behavior and consequently the macro-mechanical behavior of rock. Three types of grains – rigid, elastic, and breakable grains – are considered in this study to explore the influence of grain properties on the mechanical behavior of rock. Equivalent 2D plane strain problems are solved using 3DEC to reduce computation time. A non-uniform distribution of grain size is used to generate numerical models using Neper, a software package for polycrystal generation and meshing. A comprehensive parametric study of properties of contact and grain of the three types of grains is conducted and calibration procedures are suggested for numerical modeling. The modeling results indicate that both the contact and the grain properties affect the macroscopic mechanical behavior of synthetic rock specimens. All the three types of grains produce reasonable results for pre-peak deformation (E and υ) and macroscopic strength (UCS, σt, C and ϕ) parameters. Each grain type has advantages and disadvantages in numerical modeling. Rigid grains cannot produce volumetric strain properly and a near-zero residual friction angle of contact is needed to capture post-peak deformation behavior due to the grain interlocking effect. Elastic grains also need a very low residual friction angle of contact and brittle rock deformation behavior cannot be captured. The complex calibration procedure and long computation time are the main issues of breakable grains, although it simulates well the volumetric strain, does not require a very low contact residual friction angle, and captures brittle rock behaviors better than other two types of grains. The findings from this study are useful for rock failure process simulation using the 3DEC-GBM modeling approach.