Gangue-Cemented Fill in Goaf to Control Surface Subsidence During Longwall Mining: A Case Study from the Huaheng Coal Mine, China

Surface subsidence can cause both damage to infrastructure and a number of different environmental problems. These include surface water accumulations, loss of farmland, cracks and other damage to roads and bridges, and, in the most severe cases, the collapse of house and other buildings. Surface subsidence can be especially severe during and subsequent to coal mining. Gangue-cemented fill in goaf (GCFG) has been proposed as an effective measure to control surface subsidence during longwall coal mining. In this study, GCFG was used for an industrial-scale filling test at the 61,303 working face in the Huaheng Coal mine, China. To perform the filling test, a new GCFG storage and transport system and a system for mixing the cemented gangue were designed. The test showed that GCFG can effectively reduce the load on pillars, the amount of hydraulic pillar ram descent, and roof subsidence. This means that GCFG can effectively control the movement of the strata overlying the coal seam and therefore reduce or eliminate surface subsidence. Future research on GCFG technology should include the long-term strength and the rheological behavior of the cemented gangue.