Study of Characteristics of Surface Subsidence in Longwall Coal Mine under Poor Ground Conditions in Indonesia

This paper aims to study the characteristics of surface subsidence induced by longwall mining under poor ground conditions in Indonesia by means of numerical simulation techniques using finite difference code “FLAC3D”. The effect of mining depth in cases of single panel and multi-panel longwall mining, the influence of panel and pillar widths, and the impact of backfilling material, were incorporated into the FLAC3D software. The simulated results indicated that the angle of draw and maximum surface subsidence were significantly associated with the depth of mining, the number of extracted panels, the width of panel and pillar, and the type of backfill. In single panel mining, the largest maximum surface subsidence is observed in case of the shallowest mining depth, and it gradually decreases as the depth increases. In contrast, the angle of draw increases with increasing the mining depth. In multi-panel mining, the angle of draw and maximum surface subsidence increase as the mining depth increases. Moreover, the angle of draw and maximum surface subsidence decrease when the narrow panel and large pillar widths are adopted, and the backfilling materials are applied.