Modelling the loosening of rock in the experimental rock mining method

Analytical description of the process of rock discontinuity caused by the operation of an experimental cutting head, in which a combination of cutting and loosening methods was used, is presented. Loosening of the rock fragment takes place after reaching the tensile or shear strength of the rock, what is more favourable compared to the classical mining methods. An analytical model of the stress in the crack initiation plane was developed using the models of rock loosening using the disc tools and relationships formulated in fracture mechanism. The special integral of the differential equation of the loosening line was determined by geometric integration. Numerical simulations of the chip loosening were also carried out using the model of the solid rock built using the Finite Element Method. The developed models of losing the rock continuity were used in numerical simulations of loosening the rock fragment to analyze the impact of the selected parameters of the mining technology, of the rock properties and geometrical features of the experimental cutting head, on the shape of the loosening line and its extend. Using the stand test results, the qualitative compliance of the shape of the loosening line, determined using the analytical model and the numerical model, with the geometrical features of the rock chips obtained in the laboratory, was confirmed. It was found that the proper selection of the design features of the cutting head, such as: a small angle of the loosening disc and a small angle of inclination of the head axis, cause a qualitative increase in the loosening range.