Stability analysis of cemented paste backfill false roof in highwall mining: a case study

The highwall mining technique is widely used to extend the life of open-pit mines without disturbing the surface dwellings, while maintaining economy and productivity. In this paper, the theoretical analysis, numerical simulation and material testing methods were used to study the damage form of the false roof in Juhugeng No. 7 mine with highwall cemented paste backfill (CPB) mining of Qinghai Yanhu Group. The CPB strength effect on the false roof stability and its control are investigated in detail. The results show that the main failure mode of the false roof is breaking failure, which is mainly affected by the strength of the CPB. The simulation study found that when the strength of CPB is increased from 0.5 to 1.5 MPa, the stress of the false roof is reduced to about 1/3, and the vertical displacement is decreased from 6.8 to 4.4 mm. When the strength is changed to 3.0 MPa, the vertical displacement is further reduced to around 50%, and the vertical stress and the surrounding plastic zone are greatly dropped correspondently. It can be seen that the strength of the CPB is essential to ensure the stability of the false roof. Furthermore, the preliminary tests of the filling material show that the cement dosage, rock fineness and mass concentration have significant effect on improving the quality of CPB and guarantee the stability of false roof, it is conducive to the safe and efficient exploitation of the slicing mining with CPB.

Automated summary

The study demonstrates the significant impact of CPB strength on the stability of the false roof, reducing stress and displacement and ensuring safety during mining operations. Additionally, preliminary tests show that factors such as cement dosage, rock fineness, and mass concentration play key roles in improving CPB quality and supporting the stability of the false roof.