Research and application of roadway backfill coal mining technology in western coal mining area

In China’s western coal mining area, the traditional room mining technology is facing coal pillar instability, mine earthquake, large-area roof subsidence in the goaf, surface subsidence, water and soil loss, vegetation deterioration, and other environmental problems. To solve the aforementioned problems and to improve coal recovery, the roadway backfill coal mining (RBCM) method was proposed as a solution and its technical principle and key equipment were presented in this paper. In addition, the microstructure and mechanical behavior (strain-stress relation in confined compressive test) of aeolian sand and loess backfill materials were studied for a rational backfill design for underground mines. Further, coal pillar stress, plastic zone change, and surface deformation of the RBCM schemes were studied using the FLAC^3D numerical simulation software, and a reasonable mining scheme of “mining 7 m and leaving 3 m” was determined. The engineering application in Changxing Coal Mine shows that the RBCM method with loess and aeolian sand as backfill materials allows a stable recovery of coal pillars with a recovery ratio of more than 70 %. The maximum accumulated surface subsidence and the maximum horizontal deformation were measured to be 15 mm and 0.8 mm/m respectively, indicating that the targeted backfilling effect can help protect the environment and also control surface subsidence.