Abstract
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.
Highlights
Coal has been used as fuel in many major industrial sectors, such as electricity generation, steel and cement productions, and other manufacturing activities
The magnitude of surface subsidence is normally less than the thickness of extracted coal seam, due to some voids have been left within the goaf
Many factors affect the extent of surface subsidence such as rock mass strength, panel and pillar widths, and mining depth
Summary
Coal has been used as fuel in many major industrial sectors, such as electricity generation, steel and cement productions, and other manufacturing activities. Indonesia is one of the world’s largest coal producers and exporters. The coal production of Indonesia has increased significantly in the past years (Figure 1). The coal production in Indonesia is mainly from the surface mining method. The environmental impacts and protections have challenged the new development of surface mining, especially where the coal seams are located beneath agricultural areas, protected forests, and man-made structures. Some underground mines have been being developed and operated in order to meet the increased demands of coal production in the country (Takamoto et al, 2014; Sasaoka et al, 2014). A longwall mining is the most popular coal extracting technique by underground mining in Indonesia
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