Abstract Indonesia is the second largest coal exporter to Japan. Almost all the coal is produced from open cut mines. However, a great deal of coal is left in the highwalls of the mined-out pits. The use of highwall mining systems has increasingly come into play in the US and Australia, when overburden depth exceeds economical recovery in open cut mine. However, the stability of the highwalls is always a major safety concern in such mining. This paper describes the characteristics of the highwall mining system and discusses the appropriate highwall mining system for use in Indonesia.
1. Introduction Indonesia produces over 400 Mt of clean coal and is the second largest coal exporter to Japan, accounting for about 32 Mt of coal annually. Over 99% of the coal produced in Indonesia comes from surface mines. More open cut mines will be developed and more coal will be mined in order to fill the great demand both in Indonesia and the rest of the world.
In open cut mines in Indonesia, there are many sites where mining operations have developed long highwalls which have been abandoned due to the current economics. Mining operations have been transferred to lower stripping ratio blocks of coal or overlying seams. In some cases, coal lies buried beneath spoil heaps or is covered with mud and water. It is estimated that there is a great deal of coal beneath abandoned and working highwalls. Considering these situations, it seems to be worth introducing highwall mining systems into Indonesian open cut mines.
Final highwalls of open cut mines can form the starting point for other mining methods, such as highwall or underground mining. In its basic application, highwall mining is a technique utilized after an open cut portion of a reserve has been mined, sometimes prior to the introduction of underground mining (Seib, 1993). In this system, the coal seam is mined by remotely operated equipment, such as an auger machine or a modified continuous miner incorporated into a highwall mining system. Major issues of highwall mining systems are less coal recovery due to leaving coal as the pillars and the instability of openings and highwalls due to the pillar and roof failures.
This paper describes the characteristics of the highwall mining system and discusses the appropriate highwall mining system for Indonesia.