Control Effects of Five Common Solid Waste Backfilling Materials on In Situ Strata of Gob

Solid backfill mining as a green mining method has already been successfully applied in many mine sites. Higher requirements for the backfilling materials have been put forward in special regions, such as shallow coal seams, ecologically susceptible areas, and sites with building on the surface. The control effects of common backfilling materials on in situ strata of gob need to be studied and compared to ensure the suitable materials are applied in the mine. The meso-structure, stress variation, energy dissipation, and backfilling effects of the five common solid backfilling materials, which are Aeolian sand, gangue, mineral waste residue, coal ash, and loess are analyzed in this paper. The results show that the Aeolian sand and gangue are densely packed and internally hard when compared to other backfill materials. The deformation of the five materials to absorb the same amount of energy in the order of higher to lower was determined as Aeolian sand, gangue, mineral waste residue, coal ash and loess. The Aeolian sand’s strain energy density is 1.67 times larger than the loess, however, the Aeolian’s strain energy density in front of working face is just 32.2% of the loess, which is important to ensure the safety of the working face. The stress changes were monitored in situ with Aeolian sand and gangue as backfill materials. The monitoring results show that the Aeolian sand stress increase rate is quicker than gangue, which can support the roof effectively.