英文原文Geological and geotechnical aspects of undergroundcoal mining methods within AustraliaB. Scott P. G. Ranjtih S. K. Choi Manoj KhandelwalAbstract : About one quarter of the coal produced in Australia is by underground mining methods. The most commonly used underground coal mining methods in Australia are longwall, and room and pillar. This paper provides a detailed review of the two methods, including their advantages and disadvantages, the major geotechnical and operational issues, and the factors that need to be considered regarding their choice, including the varying geological and geotechnical conditions suited to a particular method. Factors and issues such as capital cost, productivity, recovery, versatility and mine safety associated with the two methods are discussed and compared. The major advantages of the longwall mining method include its suitability for mining at greater depth, higher recovery, and higher production rate compared to room and pillar. The main disadvantages of the room and pillar method are the higher risks of roof and pillar collapse, higher capital costs incurred as well as lower recovery rate.Keywords : Longwall Room and pillar Geological GeotechnicalIntroduction :Mining in Australia is a significant primary industry and contributor to the economy of Australia and encouraged immigration to Australia. Many different ores and minerals are mined throughout the country. With the increase in coal demand and growing awareness towards sustainable development, the coal industry has drawn a consensus over the need for increased production from underground coalmines. Around the world, the majority of coal reserves are recoverable using underground mining techniques. At the moment, almost two-thirds of coal production comes from underground mines, however, in Australia this statistic is significantly lower (ACA 2006). Currently in Australia, the majority of underground coal mines are located in New South Wales and Central and Western Queensland, where thinner black coal seams suit the underground mining methods.There are a number of different types of access modes for underground mining. These include drift, incline/ decline and shaft, and can be used in conjunction with either of the three modes for underground mining within Australia. Drift is generally used when the coal deposit is inside of a hill, and mining is undertaken by entering directly into the hill (Ghose 1984). Incline/decline is created at the ground level of a valley, where an adit is constructed and slopes down to the coal. Shaft is used with an elevator, which stretches from the surface to the coal seam underground (Wilson 1983).The main aim of the paper is to identify and compare various techniques used for coal extractions and the selection process of those techniques for a particular site based on geological, geotechnical and other factors. The two major methods of underground mining within Australia and around the world are room and pillar and longwall mining, and these two methods will be discussed in details below.Current states of Australian underground and open-cut coal mining operationsIn order to gain an understanding of the current state of coal mining operations in Australia, a broad overview is given before method suitability for coal mines is discussed.In Australia, open cut mining produces the most amount of coal for both export and internal uses. In 2004 for example, 81.5 million tonnes of coal was mined using underground methods, whilst 296.3 million tonnes were obtained using methods within an open cut system (University of Wollongong 2006). This is of no surprise as nearly two-thirds of all operating mines within Australia are open cut, as can be seen from Table 1 and Fig. 1 below.Table1 Type of mines operating within Australia (GNSW 2006;GSA 2006; GWA 2006; GT 2006; GV 2006; GQ 2006)Mine types by stateStateUndergroundSurfaceTotal coal minesQueensland103040New South Wales272552Western Australia066Tasmania123Victoria178South Australia011Total3971110Fig.1 Map of Australian coal basins (DPMC 2006)Within Australia, brown coal is typically found in the southern part, with black coal found in the basins of New South Wales and Queensland. Before proceeding further, a quick overview of coal rank and classification is given. Typically, coal rank is classified into three distinct categories depending on the degree of metamorphism that the coal forming material has endured as it matures from peat to anthracite. These are lignite, sub-bituminous and bituminous, and the properties of these greatly influence the type of method used to exploit the coal.As mentioned, surface mining or opencast mining is the predominant method used in Australia. Opencast mining on a large scale first commenced in Australia in the 1960s, where imported draglines were the main means of stripping overburden. This method c