3D numerical modelling of rock fracture with a hybrid finite and cohesive element method

To investigate the rock fracture, penetration force, and chip shape during rock breaking with a conical pick, a 3D numerical model was developed by inserting cohesive elements into finite elements. Mixed-mode cohesive traction response was applied to describe the micromechanics of rock cementation, which was also able to reflect the rock damage process and crack propagation associated with the zero-thickness elements. Simulations of Brazilian disc tests and uniaxial compression tests were used to verify the proposed numerical model and obtain rock micro-parameters, and a comparison of the penetration forces in the experimental and simulation results confirmed the accuracy and efficiency of the proposed method. Similar to the experimental phenomena of rock fracture with a conical pick, the rock crushing zone, microscopic radial cracks, macroscopic dominating crack, and main chip were produced successfully with the numerical model. Quantitative analysis of the rock fracture features (penetration force and chip shape) and breaking parameters of the conical pick revealed some valuable relationships between them, which can provide useful information for the optimal design of conical picks or breaking devices with multiple conical picks for mechanical excavation.