Study on physical and mechanical properties of oil shale ash–based green mining filling materials

The utilization of oil shale ash in developing environmentally sustainable filling materials for subterranean mines presents a promising ecological approach, albeit with typically low ash content. In this study, the filling material was prepared by adding oil shale ash and slag. The study examines the physical and mechanical properties of filling materials predominantly composed of oil shale ash slag, sourced from the Baoming open-pit mine in Jimusar, Xinjiang. Comprehensive testing and analysis are conducted to examine the chemical composition, mineral composition, and particle grading of oil shale ash, cement, and fly ash. The research prepared 45 cubic specimens measuring 50 mm × 50 mm × 50 mm and analyzed their mechanical responses under uniaxial compression conditions, employing varying dosages of ash, cementitious materials, and water as critical variables. The results indicate that the primary constituents of oil shale ash are silica (SiO₂) and aluminum trioxide (Al₂O₃). When the oil shale ash content ranges from 60 to 70%, with a cement-fly ash ratio of 7:1 and a water content of 11%, the filling material attains its highest average compressive strength of 16.37 MPa at 28 days. Furthermore, increased cement content in the cementitious material correlates with higher compressive strength in the filling material. This research underscores the potential of oil shale ash–based green mining filling materials to restore goaf.