Acceleration of ice particle in the ice abrasive water jet and its rock breaking performance by numerical simulation

In order to effectively increase the permeability of coal seams, strengthen the gas drainage of coal seams， a new technology of jet slotting coal seam using ice abrasive to replace conventional abrasive is firstly proposed in this paper. This technology may resolve the problems of blocking gas seepage channels such as pores and fissures,and sticking drill due to the increased friction resistance of hole wall,which are encountered in the application of conventional abrasive jet slotting coal seam. However,the acceleration and rock breaking performance of ice abrasive water jet remains unclear due to the discrepancy between ice abrasive and conventional abrasive. Theoretical deduction method was applied to study the acceleration and velocity distribution of ice particles. Then,a numerical model was established to monitor ice abrasive water jet breaking coal rock. It indicated that ① the acceleration of ice particle takes on a first increasing and then decreasing tendency since mixing with highspeed fluid. The final velocity of ice particles can nearly reach the pure water velocity,which can extremely increases the impacting kinetic energy of ice abrasive. This result can provide the velocity value for The numerical model.② The numerical simulation results show that a V shaped coal broken pattern appears and the ice particle melts after impacting on the coal rock. These results meet well with the findings of the previous literatures and the engineering projects,which reflects that the numerical model in this paper is suitable.③ The longitudinal crushing depth of coal rock increases linearly with the jet velocity,while the transverse crushing width takes on a first increase and then flat tendency with the jet velocity. The longitudinal damage depth is approximately 1.13 times of the longitudinal crushing depth.④ The longitudinal crushing depth as well as the transverse crushing width drastically increase ever since the mixing of ice abrasive and the increasing tendency slows down with the increase of ice abrasive concentration. The transverse damage width can reach 1.3 times of the transverse crushing width.⑤ The confining pressure extremely inhibits the longitudinal crushing depth of coal rock under the impact of ice abrasive water jet,whereas the transverse crushing width doesn′t change with the confining pressure. The study results of this paper can provide some theoretical supports for the application of ice abrasive water jet slotting coal seam. In addition,the findings in this paper can improve the theory of abrasive water jet breaking rock.