An Investigation on Optimal and Safe Design of Highwall Mining Panel Beneath Jointed Overburden Strata Using Discrete Element Modelling

Abstract

When the mine boundary is reached during surface mining operations, and conventional opencast mining becomes impractical to proceed further, a significant amount of coal reserve is left trapped under open-pit highwall. To overcome these challenges, the Highwall mining method can be seen as a viable option to increase coal production from previously operated opencast mines by extracting the trapped coal reserves and exploit thin seams that were left unmined due to economic limitations. In highwall mining, the safety and stability of a Highwall panel rely heavily on scientifically-designed dimensions of openings, web pillars, and barrier pillars. Pillar dimensions are determined using empirical formulae suggested by various researchers. However, designing highwall mining panels becomes challenging in cases where there is a presence of jointed rock mass in the overlying overburden strata, making it difficult to rely on available empirical formulas. In this study, a 3D discrete element model of a Highwall panel has been prepared incorporating the presence of jointed overburden rock mass using 3DEC™ software. Factor of safety for the overall highwall structure was determined based on observations of different combinations of web pillars, barrier pillars, and opening size. Based on which optimal and safe design of Highwall mining panel has been recommended.