This study determines the safety-stability factors of the waste dump benches at different heights and analyses the deformation law, stress variation, and crack propagation characteristics of typical slope models. The meso-mechanical parameters obtained by discrete element numerical simulation are modified through slope radar monitoring data. The results show that the critical height of the dumping benches of the studied open-pit mine is 60 ~ 70 m, and the amount of bench settlement is positively correlated with the height of the benches. After the critical height is exceeded, the bench forms a three-wedge failure due to uneven settlement.

The pressure slope toe support of the inner dump bench can reduce the deformation of the end-slope after steep end-slope mining, and the bench parameters are vital for the stability of the end-slope. This research proposes a discrete–continuous coupling calculation method and establishes the gradation curves of laboratory tests and simulations employing particle size sieving and similar gradation method. The meso-mechanical parameters of the particle model were also derived by employing the repose angle test, triaxial compression test, and simulation. On this basis, discrete elements were used to establish the inner dump loose slope and finite difference mesh to the end-slope rocky slope. Next, the effect of the change of the parameters of the inner dump bench on the displacement of the end-slope and the deformation characteristics of the bench itself was analyzed. The results show that the presence of a bench can significantly restrain end-slope deformation. As the bench height increases, its effect on the end-slope displacement decreases. When bench height remains constant, end-slope displacement gradually becomes uniform with increased bench width. Finally, this study divides the deformation of the bench into “extrusion region”, “slip resistance region”, and “self-slip region”, with the slip resistance region being the key to bench stability.

The instability of geological slopes in mining environments poses a significant challenge to the safety and efficiency of operations. Waste Dump#2 at the Ziluoyi Iron Mine in China is a notable case study that highlights the challenges associated with sizable base slopes and large step heights. To address hidden hazards in the mine and the above issues, an inclusive investigation is carried out to examine the physical and mechanical properties of the soil–rock slope through indoor testing and analyze the deformation mechanisms of the slope using numerical simulations, taking various factors into account. The study reveals that the stability of Waste Dump#2 is deeply affected by weight, groundwater conditions, earthquake loading, and rainfall. To this end, the cohesion and internal friction parameters of the soil–rock slope are first determined through direct shear tests, which show a cohesion of 6.215 kPa at the top of the slope and an internal friction angle of 34.12°. By adopting GEO-SLOPE, 3D Mine, and AutoCAD software, stability calculations of the slope are performed, which give stability coefficients of 1.547 under normal conditions, 1.276 in rainfall, and 1.352 in seismic conditions. These results meet safety standards and ensure the safe and efficient operation of the mine.

This study presents different land saving and loss reducing schemes. Comprehensively compare the economic benefits of the schemes. It is shown that the optimal scheme can recover tons of coal resources on the south slope, creating significant economic benefits. Numerical simulation was utilized to analyze the changes of slope stability, deformation, and shear strain increment in the process of land saving and loss reducing. Results found that the slope stability decreases rapidly, and the toe of the slope has to be internally discharged in time to compress the slope. Timely follow-up of in-slope rows can improve slope stability. The position of the slope shear exit changes with the increase of the distance of the inner row, and its stability increases gradually. When the distance of the lower inner row exceeds 120 m, the increase of the internal row distance has little influence on the slope stability. When the inner distance exceeds 60 m in the process of internal dumping of upper platform, the position of potential sliding plane gradually changes from the lower dump to the upper and lower dump with the increase of inner dumping distance. It shows that the stability of the dump will be damaged if the upper dump continues to be discharged. Therefore, the distance between the upper and lower dump sites is more important than 60 m. The stability of the south slope is good in the process of mining and internal drainage, and the overall stability of the south slope is controllable, based on slope radar monitoring.

Open-pit mining is a common method for extracting coal, but considerable resources are often left unrecovered at the bottom of end-slopes, leading to a permanent waste of resources. This research presents a sustainable approach of multi-layer highwall mining at different levels to address the issue of abundant resources left unrecovered at the bottom of the end-slope in thick-seam open-pit mines. The interlayer between the upper and lower entries is simplified into a beam structure model, the bending moment distribution characteristics of the beam under a load of highwall miner are analyzed, and a method for calculating the thickness range of the interlayer is proposed. The web pillar width and interlayer thickness, obtained theoretically, are verified through a numerical simulation, and the results of mining a single layer are compared to those of mining multiple layers. The results show that the web pillar width and interlayer thickness derived from the numerical simulation are basically the same as those of the theoretical analysis. Compared with single layer mining, the vertical stress on the web pillar in the lowest panel is reduced by 14.83~18.25%, and the safety factor of the web pillar is increased to 0.27. The web pillars and interlayers at different elevations are stable during multi-layer highwall mining. These findings support the feasibility of multi-layer highwall mining for resource recovery, which is conducive to sustainable mining.