A grain-based model considering pre-existing cracks for modelling mechanical properties of crystalline rock

Abstract

Mechanical properties of crystalline rock are greatly affected by its micro-structures which are characterized as highly-interlocked polygon grains and presence of micro-defects. Due to insufficient consideration of micro-structures in crystalline rock, previous simulations using discrete element method (DEM) cannot realistically reproduce the mechanical properties of crystalline rock including crack closure behaviour and high ratio of uniaxial compressive strength (UCS) against tensile strength (TS). The irregular shape of minerals in crystalline rock is modelled by discrete element method (DEM) using grain-based model (GBM). Presence of initial cracks is incorporated into GBM by introducing two notional contact surfaces to model gradual closure behaviour under compressive loading, and to obtain a higher UCS/TS ratio. The stress-strain response and crack evolution including crack closure, crack initiation, crack coalescence as well as development of macroscopic shear failure can be realistically reproduced with the proposed model. A calibration procedure is proposed to match properties of Remiremont granite under room temperature. The influence of initial cracks on the rock is then comprehensively studied. The simulation results show a good agreement with the experimental outputs under various treatment temperatures. By modelling the polygon grain and pre-existing cracks, the simulated UCS/TS ratio can be more realistic and increased up to a value of 49.