Flat-joint model to reproduce the mechanical behaviour of intact rocks

The mechanical behaviour of intact rock materials is controlled by properties of grains and cementation (bonding) between grains. In the particle flow code (PFC), three main bonding approaches namely contact bond (CB), parallel bond (BP) and flat-joint (FJ) models have been used for simulation of bond between particles. This article firstly investigates the ability of these bonding approaches in reproducing the mechanical behaviour of intact rocks through a comparison against laboratory experiments undertaken on Hawkesbury sandstone. The results show that the FJ model, unlike CB and PB models, is able to reproduce the mechanical behaviour of Hawkesbury sandstone under different loading conditions. As the effect of micro-parameters of the FJ model on the laboratory-scale mechanical properties is not well-understood, a comprehensive parametric study was undertaken. The results show that the tensile strength of material is mainly controlled by the FJ-bonded fraction and the FJ tensile strength whereas several micro-parameters control the uniaxial compressive strength due to contribution of both tensile and shear cracks in the failure mechanism. Finally, a new calibration approach was suggested to ease the determination of micro-parameters and minimise the iteration process.