Study on top-coal migration law and reasonable top-coal caving parameters in fully-mechanized top-coal caving face

In order to study the migration law of top-coal in top-coal caving process of top-coal caving in coal seams with different dip angles and determine the reasonable coal caving parameters, PFC2D particle flow software was used to simulate the top-coal migration law under different dip angles of No.10301 working face of Jining No.2 Coal Mine. Combined with the field measurement method, the reasonable coal-discharging parameters was determined, and the influence law of the caving ratio, the coal caving step distance and the angle of the mining on the top-coal release rate were obtained. The results show that the larger the angle of the mining, the longer the displacement distance of the top-coal from the initial position to the coal inlet;the larger the vertical mining angle is, the longer the displacement distance of the top-coal from the initial position to the coal opening;the easier it is for the top-coal to move to the gob, the lower the release rate of the top coal;with the increase of the inclination of the support, the "force chain arch" effect formed by the interaction between the top-coal and the support during the migration process is more obvious;the optimal mining height of the No.10301 working face of Jining No.2 Coal Mine is determined to be 3.5 m, the optimal top-coal caving step distance is 0.8 m, the optimal mining and caving ratio is 1∶3, and the optimal coal caving gangue ratio is determined to be 7%;the simulation results are similar, verifying the feasibility of numerical simulation.