According to the Commonwealth of Australia (2016), there are around 70 operating underground rock mines active within Australia. The majority of underground mines are located in Western Australia, Queensland and NSW, with only a few spread throughout South Australia, Northern Territory and Tasmania.
Currently, one of Australia’s largest underground mine is Newcrest’s Gold, Silver and Copper Cadia Valley Operations, near Orange in NSW. It is estimated that the mine has proven contained metal reserves of approximately 37 million ounces of gold and 8.2 million tonnes of copper. Cadia’s mine alone has employed over 1900 direct and indirect jobs proving a fundamental role in the region’s economy and the lives of many residents in and around the area. In 2018 alone, the mining industry in NSW across the Central West injected approximately $868 million into the Australian economy and has been described as the “bedrock of economic stability to many areas around Orange. Across the border, Queensland is home to one of the largest coal basins in Australia, the Bowen Basin. Due to the quantity of concentrated ore in the area, it has triggered heavy investment in Queensland’s coal mining industry. The Bowen Basin contains over 34 billion tonnes of extremely high-quality coal. Currently, Queensland still has 5 operating underground mines, with a gross raw production of approximately 42 million tonnes of commercial coal/yr from underground mines alone, mostly coming for the Bowen Basin. With approximately $21 billion being injected into the Australian economy from the export of Queensland’s coal every year.
The Australian mining sector is one of the most profitable businesses in Australia and has a strong influential impact on our nation’s budget. Every year Australia exports a large proportion of the materials mined, such as Iron ore, coal, petroleum gases and gold worldwide, that supports the growth of our nation’s economy. There are hundreds of companies around the nation that deal with the various aspects of the mining industries, with over 200 companies alone supplying just specialised products and services to underground mines. The mining industry plays an important part in supporting these small businesses across all of Australia. The services required to maintain such a vigorous industry varies widely, from software updating to numerical modelling to design to drilling to recycling to safety and handling, which varies with every mining process.
Biggest underground mining operations in Australia
- Newcrest’s Cadia East operations in New South Wales.
- BHP Billiton’s Olympic Dam operations in South Australia.
- South 32’s Cannington operations in Queensland.
- Rio Tinto operations in Queensland and New South Wales.
- Anglo American Australia’s Callide operations in Queensland.
- Glencore plc operations in New South Wales and Queensland.
- Peabody Energy’s operations in Bowen Basin, Queensland.
- Fortescue Metals operations in Western Australia.
Primary Methods of Underground Mining
Sub Level Caving:
It is currently one of the most innovative mining methods in the industry. This method of mining is usually implemented when it is no longer viable to mine in an open mine. The procedure involves drilling vertically downwards directly into the ore. This is followed by drilling sub levels horizontally at consistent intervals (as shown in figure 1). Once sub levelling is completed, a series of circular patterned blasts are detonated from each level and the demolished ore is excavated.
Sublevel caving focuses on maximises the efficiency of mining practices by ensuring the maximum quantity of ore is excavated, without interfering with other projects on other sub-levels.
It is the process of excavation of an ore body via detonation and leaving an area called a stope. This process is only utilised when the structural integrity of the surrounding rock is sufficient. One stope can produce over 25,000 tons of ore /month.
This mining method is relatively safe as the mine retreats away from the previously mined or unsupported area of the underground mine. With this form of mining requiring repetitive techniques, safety training is easily implemented. However, by utilising this method it does increase the risk to ore dilution, however, 100% of the ore is usually retained in these situations with the current innovative technologies available.
It is the underground version of open pit mine. It focuses on undermining the ore at locations where it will compromise the structural integrity of the ore to force it to collapse under its own weight. Once the compromised and has fallen, it is excavated by machinery. This method is effective as it usually requires only 10% of the running cost of conventional methods of mining, and production rates can reach up to 100, 000 tonnes per day.
Cut and Fill Mining:
It is one of the most utilised mining methods in the industry, which relies on a simple cutting of the ore, excavation and filling. The ore is cut into different sections and removed via controlled detonations. The voids created by the detonations are filled usually with waste rock/tailings or cement. However, this method of ore excavation can be quite economically costly.
It follows a similar method to cut and fill, however rather than detonating and refilling, the area exposed is left open as a platform for the next level, and acts as a support for wall stability of the slope. This method selectively isolates concentrated areas of ore bodies which heavily reduces dilution.
Room and Pillar:
It is a process primarily utilised for flat-lying or dipping ore bodies. The method includes creating open areas within the ore body and installing pillars of rocks at consistent intervals throughout the open area to support the rock structure above. After mining out the ore within the area the pillars are removed for safe collapse and fill to take place
Large coal blocks are identified underneath the earth’s surface and usually fit in the dimensions of 100-300m in width by 1000m to 3000m in length. This block of coal is then extracted in slices by undercutting, where it is then blasted and drilled. The remnants are placed on conveyor belts until the entire block is extracted. The roof is supported by longwall shields which provide cover for the conveyor belt, workers and machinery. Through the use of longwall shearers production rates reach approximately 20 000 tonnes/day.
The mining industry has been developing its methods and processes for hundreds of years. As more efficient, effective and robust technologies enter the market, the industry continues to expand, and push its limits. However, a consequence of these advancements and adaptation of new processes is that along with these changes there must be changes in health and safety considerations. This is to ensure that the workers that are involved in this industry are re-assured that no health impacts result from working in a mine environment.
In the upcoming articles, health and safety aspects of the current underground mining methods will be discussed in detail to understand how and why such stringent mining practices were introduced, and what kind of impact these changes have had on the industry on a national scale. As medical research continues to improve, studies have shown that chemicals and materials that were once not considered dangerous, do in fact cause harmful effects on the human body. As these perspectives change in the industry, the health and safety consideration must also be adjusted. Safety is the most important aspect of mining, due to the exposure to high-risk situations, which can be fatal in some circumstances, and minimising this risk to miners is the primary focus.
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- Mining Technology, 2014, Newcrest Mining Opens Australia’s largest underground gold mine, https://www.mining-technology.com/uncategorised/newsnewcrest-mining-opens-australias-largest-underground-gold-mine-4273127/
- Newcrest Mining Limited, 2014, Australia’s largest underground mine opened by NSW premier, http://www.newcrest.com.au/investors/market-releases/australias-largest-underground-mine-opened-by-nsw-premier
- Austrade and Commonwealth of Australia, 2016, Underground Mining, https://www.austrade.gov.au/articledocuments/2814/underground-mining-industry-capability-report.pdf.aspx.