Air Flow Movement Law in Working Face and Gob with Roof-Cutting and Pressure-Releasing Mining: A Numerical Simulation and Engineering Verification.

Abstract

In comparison to traditional longwall mining, "roof-cutting and pressure-releasing" mining along gob-side entry retaining changes the permeability of the gob, as well as the pressure-relief characteristics and caving mode of the overlying strata. These changes are a result of the interaction of these factors, which also changes the boundary condition of the gob and the airflow movement law of the working face and the gob. In order to study the law of air flow movement in the working face and gob under the "roof-cutting and pressure-releasing" mining along gob-side entry retaining, the permeability model of gob was established under the engineering background of the 21,304 experimental working face of Chengjiao coal mine, then using fluent numerical simulation software, the movement law of air flow in working face and gob is simulated. The results show that the law of air leakage is much different from that of traditional longwall mining, and there are two main air leakage routes, First, most of the airflow will flow directly into the gob-side entry retaining under the action of inertia, and it will collide with the air flow provided by the fan at the end of the gob-side entry retaining, and the air will leak in the gob along the airflow direction; second, when the remaining airflow flows to the working face, the air leakage is serious in the air inlet corner, and most of the air flow flows into the gob. In view of the air leakage area, the air leakage prevention measures are put forward, such as setting the baffle plate, hanging the wind shield at the corner, and blocking the wall of the roadway with guniting; the simulation results show that the air leakage area is obviously reduced, and it is consistent with the measured data. The simulation results can generally describe the law of air flow movement in the face and gob with "roof-cutting and pressure-releasing".