Yanli Huang

Impact law of the bulk ratio of backfilling body to overlying strata movement in fully mechanized backfilling mining

Fully mechanized backfilling mining technology with waste, fly ash, and loess, etc. provides advantages of safety and high efficiency to the extraction of coal under buildings, railways and water bodies. In this paper, the bulk ratios of backfilling bodies with different waste and fly ash mixture ratio was analyzed with MTS815.02 electro-hydraulic servo rock mechanical testing system and compacting device, the optimal mixture ratio of waste and fly ash was determined, and it proposed that the backfilling body should be firstly compacted after being backfilled into the goaf. With numerical simulation, the impacts of bulk ratio of waste and fly ash backfilling body to overlying strata movement law and surface subsidence controlling in backfilling mining were analyzed, and it figured out the bulk ratio of backfilling body that could ensure a reasonable range of surface subsidence. Finally, the engineering application confirmed that the strata movement controlling in fully mechanized backfilling mining was more effective, the surface buildings and facilities were not severely influenced. The above achievements could provide technical reference for the successful implementation of fully mechanized backfilling mining.

Test on mechanical properties of solid backfill materials

Abstract In this paper, characteristics that the overlying strata movement is controlled by solid backfill materials are illustrated in the coal mining with solid backfilling method. In addition, the mineral and chemical composition, density and moisture content of waste rock and fly ash are tested and analysed by physical–chemical treatment. By investigating the compaction deformation and time-dependence characteristics under different ratios of waste rock to fly ash, the optimal ratio of the mixture is obtained to achieve the smallest deformation, and results show that deformation mainly occurs in the initial period of loading. Combining the results of density test on site backfill materials, it indicates that the mass ratio of backfill materials to coal mining is 0·83 in order to ensure the effective of controlling the overlying strata in the coal mining with solid backfill method. The findings of the research provide references for the selection of solid backfill materials in coal mining.

Effect of Particle Size on the Energy Evolution of Crushed Waste Rock in Coal Mines

List of symbols U Total energy U Dissipated energy U Released elastic energy U Dissipated energy for particle breakage and extrusion U Dissipated energy for friction between the samples and the compaction device r Axial compaction stress ea Corresponding strain of the axial stress r eb Remnant strain after stress unloading from the axial stress r to zero k Coefficient of lateral pressure l Frictional coefficient between the waste rock and the chamber wall D Diameter of the compaction device H Loading height of the waste rock H1 Height of the steel chamber H2 Length of the dowel bar H3 Thickness of the loading platen H4 Distance between the top surface of the dowel bar and the steel chamber