Solid Backfilling Efficiency Optimization in Coal Mining: Spatiotemporal Linkage Analysis and Case Study

In coal mining, solid backfilling technology is widely used. However, its efficiency is seriously hindered by the following two factors. Firstly, the process flow of the solid backfilling operation is more complicated in the back, and the spatiotemporal linkage (SPL) between actions of the cylinders powering each support and between hydraulic supports in the whole face lacks continuity. Secondly, the coal mining process in the front has a higher level of intelligence and technical maturity than the backfilling operation in the back, the latter permanently staying behind the former. To this end, the present study investigates the SPL of the mining and backfilling operations for single supports in the working and whole faces. The SPL of cylinder actions is analyzed for intelligent backfilling using hydraulic supports. We also investigate the SPL of the positions of each piece of key equipment involved in different steps of intelligent backfilling in the whole face. Formulas are derived for calculating the time required to complete the cyclic hydraulic support movement-discharge-filling operation for single supports and the whole face. The key factors influencing the time required to complete a hydraulic support movement-discharge-filling cycle are analyzed. On this basis, a backfilling efficiency optimization scheme is proposed. It envisages reducing the number of tampings and time gaps in actions of single supports and cylinders, increasing the number of hydraulic supports in parallel operation, and intelligent upgrading of the backfilling operation. These findings help synchronize coal mining and backfilling operations.