STUDY ON INVERSION OF COAL STRESS BY DRILLING PARAMETERS BASED ON ENERGY CONSERVATION LAW

Due to the complexity and particularity of coal mine production, predicting the coal stress is helpful to prevent coal mine accidents. Therefore, it is of great guiding significance to study the fragmentation change of coal formation for the rapid hole formation. Based on the theoretical analysis and numerical simulation, the breaking law of coal under drilling impact load was studied. The results show that during the collision process, the energy generally shows a gradual attenuation trend, and the energy is mainly converted from the kinetic energy to the internal energy. For the early stage of impacting coal, there is a compression deformation on the coal sample surface, and there are no obvious cracks around the pit. Continuous impact leads to the gradual development of internal cracks in the rock sample. With the increase of stress, the high stress area around the bit decreases relatively. This prevents the drill bit from damaging the coal body and also affects the formation of drilling holes. The torque fluctuates periodically during the drilling process. When the stress is unchanged, the peak value of torque is basically unchanged. The research results can be used as a reference for the selection of drilling technology.