Coal breaking characteristics of presplitting assisted impact pick

In recent years,the continuous large-scale mining of coal resources in China has made the overall coal min- ing more and more difficult. The increasing proportion of hard coal and viscous coal is the main factor restricting the efficiency of coal mining. However,the traditional mechanical coal breaking technology is difficult to achieve an effi- cient cutting of hard coal and viscous coal. Therefore,aiming at the problem of poor coal breaking effect of traditional pick in hard and viscous coal and rock,starting from the angle of combination of auxiliary presplitting and cutting of coal,the characteristics of impact presplitting and cutting of coal and rock are studied by means of theoretical analysis and numerical simulation. Considering the traction,rotation and impact movement in actual work,the motion trajectory model of pick is put forward and the presplitting is established. The mathematic model of coal-breaking trajectory of presplitting assisted impact pick is established,and the analytical solution of coal-breaking trajectory of pick is ob- tained. Based on the analysis results,the discrete element model of coal breaking of presplitting assisted impact pick and single pick drum with traditional pick is established. The coal breaking characteristics of the two kinds of pick are compared and analyzed from the aspects of the actual proportion of coal breaking particles,and the degree of difficulty in the coal breaking and force fluctuation of the pick. The results show that in coal breaking efficiency,the presplitting assisted impact pick increases 36% when the hardness of coal is f6. When the cohesive force is 2. 6 MPa,the efficien- cy promotion of the presplitting assisted impact pick is close to 14% . In the difficulty of coal breaking,the presplitting assisted impact pick can reduce the difficulty by 50% when the hardness is f6. When the cohesive force is 1. 88 MPa, the presplitting assisted impact pick can reduce the difficulty of about 12% . In the force fluctuation of the pick,the presplitting assisted impact pick can reduce the force of nearly 7 000 N in the hard coal or the viscous coal. Therefore, the study of the presplitting assisted impact pick will be beneficial to the crushing of the special coal rock medium such as hard and viscous.