Underground copper mine expansion
El Teniente is the world’s biggest underground copper mine and the sixth largest copper mine by reserve size. Located 80km south of Santiago in the Andes mountain range in Chile, the facility is undergoing an extensive $3.4bn expansion project called El Teniente New Mine Level project to extend its production life by 50 years.
Owned and operated by Chile’s national copper company Codelco, the underground copper mine was discovered in the early 19th century and has been operational since 1905. The El Teniente New Mine Level project will access approximately 2.02 billion tonnes of ore reserves (grading 0.86% copper) lying deeper at about 350m below the existing undercut level of the mine.
The expansion project received environmental permit in March 2011 and construction started in October 2011. It is expected to create around 3,500 jobs during construction phase and is scheduled to be operational in 2018.
The Caserones copper and molybdenum deposit in Chile features six of the top ten biggest copper mines in the world.
The El Teniente mine extracts the porphyry copper deposit, located 2,500m above sea level in the core of a volcanic mountain in the Libertador General Bernardo O’Higgins region in the Andes. Mining is carried out at different levels around a non-mineralised formation called the Braden Pipe that houses mining infrastructure of each level.
The underground mine was estimated to contain 15.2 million tonnes of fine copper (1,538 million tonnes of ore grading 0.99% copper) in proven and probable reserves at the beginning of 2013.
The existing underground mine comprises six mining bocks around the Braden Pipe at different elevations including the Esmeralda, Reservas Norte, Diablo Regimiento and Pipa Norte mining blocks.
Block caving is used for extracting ore. More than 2,400km of underground drifts and in excess of 1,500km of underground road have been developed in the mine since it began operations.
The mine is accessed by a 3.5km tunnel and the ore is hauled to the surface through a railroad system. The hauled ore is sent to the crushing plants on surface from where it is conveyed to a concentrator and the produced copper concentrate is sent to nearby smelter.
El Teniente is one of the first mines in the world to deploy semi-automated load haul dumpers (LHDs) for ore extraction in 2004. Sandvik AutoMine automated loading systems were introduced in the Pipa Norte and Diablo Regimiento sections of the mine to automate the LHD fleet.
The Chilean copper mine employs approximately 11,000 contractors and 4,000 staff workers. Amerigo is the contractor for producing copper and molybdenum concentrate from El Teniente’s tailings.
The New Mine Level (NML) project located around 1,880m above sea level will expand El Teniente’s mining operation deeper about 100m below the existing main haulage level of the mine. The structural design of the new mine allows for uninterrupted operation of the existing mine during its construction.
Mining will occur only on a large single level instead of scattered blocks on different levels as is the case with the existing El Teniente mine. The new mine will use panel caving and progressive sinking method for extracting ore. The ore will be brought to a new stockpile on the surface near the concentrator by a 2,134mm conveyer belt.
Two underground parallel tunnels, each 9km in length and 8m in diameter, and connected by 22 cross-tunnels, are being built as part of the project. One tunnel will be used for entry and exit of employees, while the other will house the conveyer belt system. In total, it will involve 98.45km of tunnels and 3.4km of vertical development for the creation of ventilation shafts and transfer shafts.
Drainage water from the mine is planned to be piped along the main conveyer belt to the surface. Intelligent ventilation monitoring system involving tags worn by operators to quantify the air requirement in a particular area will be used to ensure lesser energy consumption.
A 17km long new access road is also being developed at a lower elevation as part of the project to halve the travel time currently being taken to reach the El Teniente mine site.
The El Teniente New Mine Level Project is expected to be an automated mining operation with the mining, processing and transport activities planned to be remote controlled from a new corporate building near the city of Rancagua, located 50km away from the mine site.
The use of automation with remote control will mitigate risks associated with exposure inside the underground mine as well as allow real-time monitoring of the mine’s rock-mass behaviour.
The El Teniente mine produced 450,000t of copper in 2013 compared with 417,000t in 2012, becoming Codelco’s biggest copper producing mine during the year.
It will process approximately 137,000t of ore per day and maintain El Teniente’s the existing production level for a period of 50 years. The project also keeps the option open to expand the mine’s ore output capacity to 180,000t per day.
Sinclair Knight Merz (SKM) completed the project’s prefeasibility and feasibility studies in 2008 and 2011 respectively.
Hatch Chile, in association with tunnelling staff from Hatch Mott MacDonald in Canada/US and Mott MacDonald in the UK, prepared the reference design and contract documentation for the El Teniente New Mine Level design build project.
Constructora de Tuneles Mineros, a joint venture formed by VINCI Construction Grands Projets (60%) and VINCI’s two other subsidiaries Soletanche Bachy (20%) and Soletanche Bachy Chile (20%), was awarded a contract worth $400m in September 2011 to design and build the two main parallel tunnels along with two intermediate access tunnels totalling 6km.
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