Simulation of heterogeneity, creep, damage and lifetime for loaded brittle rocks

Abstract

A grain-based heterogeneous numerical model originated from the discrete element method is developed and applied for Lac du Bonnet granite. Basing on Voronoi cells, the modelled microstructure considers different mineral components and grain size. The model takes into account elastic grain and elasto-plastic contact deformation, inter- and intra-granular fracturing and lifetime prediction on basis of subcritical crack growth. The procedure is successfully applied to simulate uniaxial compression tests, Brazilian tests and uniaxial creep tests. The damage processes are studied in detail and Mode-I and Mode-II fracture toughness were determined. The proposed modelling allows the simulation of time-dependent behaviour in terms of the damage process during primary, secondary and tertiary creeps until the final failure characterized by macroscopic fracturing (shear band and/or macroscopic tensile fracture). All simulations have shown reasonable agreement with macroscopic results obtained from lab tests on granite, but have in addition delivered deeper insight into the microscopic damage process. The proposed modelling approach is recommended for brittle rocks.