A Novel Backfill Material for Roof Supports in the Cut-through Entries of Longwall Mining

Original scientific paper To enhance underground mining safety, researchers developed high-water and fast-setting cement (HWFSC). HWFSC essentially consists of two components and can be mixed with large quantities of water. To determine its mechanical strength, a series of uniaxial compressive strength tests were conducted on HWFSC specimens with different water-to-solid ratios. Results indicate that peak strength declined significantly with the increase in W/S ratio, whereas residual strength increased gradually with this enhancement. The feasibility of backfilling cut-through entries with HWFSC is then evaluated through a case study. The LaModel program was used to assess the yielding of the fender pillar and the deformation of the cut-through entry. Results also show that the use of HWFSC to backfill the cut-through entry addressed complicated ground control problems effectively. Further analysis also suggested that HWFSC was the optimal backfill material in terms of both economic cost and roof support safety.