Research on the Development of a Monitoring Experimental Platform for Top Coal Migration Trajectory in Longwall Top Coal Caving and Optimization of Coal Drawing Process

Abstract

Understanding the migration trajectory characteristics of top coal in longwall top coal caving (LTCC) is crucial for studying the flow properties of granular top coal, drawing laws, and optimizing the coal drawing process. To monitor the migration trajectory of top coal during the drawing process, an experimental platform was developed for monitoring the top coal migration trajectory in LTCC. Using this platform, physical simulation experiments of LTCC were conducted. A multi-step experimental procedure was designed, including "model construction, marker point installation, simulated coal drawing, data collection, and trajectory inversion." The migration trajectories of top coal at different layers during the coal drawing process were obtained, and the drawing body of top coal was inferred. Additionally, a bi-directional top coal drawing body equation was theoretically derived, establishing a quantitative relationship between the gangue content (cumulative and instantaneous) and top coal recovery. Based on this, field process optimization was carried out, adjusting the "four-level" method to a double-opening group coal drawing method. The instantaneous gangue content threshold at the coal drawing openings was set to 35%. The measured top coal recovery at the working face reached 90.12%, an increase of approximately 14.87 percentage points compared to the previous recovery. The cumulative gangue content was controlled at around 9.25%, and the coordination efficiency of coal caving reached 68.2%, which is close to the theoretically derived results. This indicates that the theory can provide certain theoretical guidance for determining relevant process parameters in coal drawing operations.