Abstract
Reliable operation of the feeding system plays a crucial role in ensuring the safe and efficient production of the working face of backfilling gob-side entry retaining (GER). In the process of vertical feeding of the roadside support body material, the problem of blocking of the feeding shaft has occurred to the test mine, which seriously affects the production safety in mines. In this paper, based on the theoretical analysis, a fluid-solid coupling numerical model was established. The change rules of the speed of sacked gangue, pressure of air below it, and speed vector distribution with different vent diameters were obtained. The blocking mechanism of the feeding system was revealed. The results show that if the exhaust vent of the stock bin was shut, the speed of gangue in the mine increased and then decreased and finally blocked in the feeding shaft. If the exhaust vent of the stock bin was opened for pressure discharge, with the increase of diameter of the exhaust vent, the maximum speed and ending speed of sacked gangue increased, pressure differential reduced, and speed vector was uniformly distributed. The energy criterion of blocking of the feeding shaft was further obtained. Based on the engineering conditions of the test mine, when the feeding shaft is blocked, the critical value of diameter of the exhaust vent is 30 mm. The research results provide basis for the design of key parameters of the vertical feeding system, ensuring the safe and efficient production of gob-backfilled GER working face.
Highlights
Gob-backfilled GER [1] is an innovative sustainable nonpillar mining technology which can adapt to a variety of complex geological conditions. e stability of the roadside support body determines the success rate of gob-side entry retaining with gangue backfilling mining
Sacked gangue is in full contact with the wall of the shaft. e air temperature in the shaft is constant. e initial condition is that they are freely placed at the wellhead and fall down by gravity. e model of the whole feeding system is shown in Figure 8. e shaft is designed in a tetrahedral mesh, and the stock bin part is designed in a free mesh
Simulation Results and Discussion e movement of sacked gangue when the stock bin is closed or has an exhaust vent with a certain size is simulated, respectively. e corresponding distribution and change rules of air speed, speed of sacked gangue, and air pressure are obtained. e law of variation of speed of sacked gangue and air pressure is fitted to a formula and substituted into the energy equation. e blocking mechanism of the feeding shaft is revealed from the perspective of the change of kinetic energy and air energy
Summary
Gob-backfilled GER [1] is an innovative sustainable nonpillar mining technology which can adapt to a variety of complex geological conditions. e stability of the roadside support body determines the success rate of gob-side entry retaining with gangue backfilling mining. Smoothed particle hydrodynamics (SPH) and discrete element method (DEM) [17] can be used to study the ow pattern when material humidity is high When these two methods are used, special attributes of materials shall be de ned, which greatly increases the calculation time and complexity. Ju et al [22] considered collision between particles in the process of movement of solid back ll material in the vertical feeding shaft. Is paper established a uid-solid coupling model with the method of theoretical analysis and numerical simulation, studied the solid movement rules and the mechanism of energy conversion of the system in the process of falling of sacked gangue, and revealed the blocking mechanism of the feeding system.
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