Stability Analysis of Multi-Layer Highwall Mining: A Sustainable Approach for Thick-Seam Open-Pit Mines

Abstract

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.

Feasibility Evaluation of Highwall Mining in Open-Pit Coal Mine Based on Method of Integrated Analytic Hierarchy Process–Fuzzy Comprehensive Evaluation–Variable Weight Theory

“…Statistics show that the maximum mining depth reached by overseas highwall mining technology is 500 m, with the highest monthly output reaching 124,000 tons. Coal mined using highwall mining machines in the United States accounts for about 4% of the country's total annual coal production [7][8][9]. However, due to varying conditions in different mines, highwall mining technology has experienced several incidents of platform instability, landslides, and significant roof collapses in practical application [10][11][12].…”

Assessment of Rock Slope Stability in a Humid Tropical Region: Case Study of a Coal Mine in South Kalimantan, Indonesia

“…Highwall mining has become a new standard practice in open-cut mining in countries like China, Australia, India, and Russia to maximise coal recovery from marginal reserves (Tian et al, 2023). Highwall mining involves extracting coal from the base of the highwall using a series of parallel entries driven into the coal seam, typically using continuous highwall mining and auger mining (Shen, 2014).…”

“…The stability of highwall mining faces problems from the slopes, interlayer between openings, and pillars; the problems become more complex when dealing with multi-seams and steeply dipping coal seams (Ross et al, 2019;Tian et al, 2023). Comparable to room and pillar mining, the loss of support from the pillar can cause instability (i.e.…”