Rio Tinto Group, 66 percent stakeholder of Oyu Tolgoi JSC, previously announced to invest USD 5 billion for the development. Over 80 percent of Oyu Tolgoi’s total value lies deep underground and the extraction cost is estimated to be around MNT 12 trillion. The company expects that 60 percent of total investment of the underground development will be financed this year. Furthermore, Oyu Tolgoi JSC plans to employ around 14 thousand workforce, which displays the intensity of the second phase development. The company recently announced that the sinking of Shaft 2 is expected soon and fit out will progress throughout 2018. Also, the sinking of Shaft 5, which progressed during the fourth quarter of 2017, is expected to be completed in the first quarter of this year. Armando Torres, CEO of Oyu Tolgoi JSC, announced to increase domestic companies’ involvement in the underground development project.

The company will be able to operate 24/7 on two shifts once the underground mine complex, which is using block-caving mining techniques, starts operation. The deepest shaft is the equivalent of 12 Blue Sky Towers in depth and is expected to progress throughout the year.

The block caving method of mining uses the force of gravity to extract ore from an underground deposit. A series of lateral tunnels are developed under the deposit with an undercut level and extraction level. The ore is undercut creating a void which allows the rock above to fall under its own weight into draw bells. Loaders on the extraction level then remove the fallen rock from the draw points, allowing more rock to feed into the draw bell and as the void created by the initial undercut propagates up through the deposit.

In addition, the company is planning to build around 10 km long conveyor, 3 maintenance shops, 2 drilling machine shops and a shotcrete station, as well as to drill 200 km long tunnels. Around 1000 subcontractor and suppliers can be involved in the underground development. Gold and copper contents in the concentrate is estimated to be tripled with the completion of the underground mine. The company is planning to start its operation by 2020 and reach full capacity by 2027. This will allow Oyu Tolgoi JSC to annually produce 500 thousand tons of copper. The company is currently producing around 175-200 thousand tons of copper annually.

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