Integrated green mining technology of “coal mining-gangue washing-backfilling-strata control-system monitoring”—taking Tangshan Mine as a case study

In Tangshan Mine, there are four engineering problems, including the layout of multiple seam mining system, serious environmental damages caused by gangue accumulation and surface collapse, nearly 100 million tons of three under coal (coal trapped under buildings, water bodies, and railways) to be released, and the control accuracy of stratum formations to be improved. The work developed the integrated green mining technology of coal mining, gangue washing-backfilling, strata control, and system monitoring. First, a production system was designed for surface-underground transportation of backfilling materials, underground gangue separation, multiple-seam combined backfilling, and mining. Second, key backfilling equipment was developed at mining heights of 2.2 and 3.5 m by backfilling system layout and precise stratum control methods in Tangshan Mine. After real-time monitoring of stope pressure, backfilling effect, and surface deformation, we evaluated the implementation effect of mining, washing, and backfilling technology. The integrated coal mining in seams 5, 8, and 9 of Tangshan Mine showed that the four backfilling surfaces of T3281, T3292, F5001, and F5002 recovered 946,000 t of raw coal and 1.18 million tons of filled gangue, with a net profit of 363.20 million yuan. The maximum land subsidence values (18, 119, 64, and 47mm) were far lower than the deformation extremes based on the requirements of surface building protection.