Our Operations

Underground Development

Oyu Tolgoi consists of a series of deposits containing copper, gold, and silver. The deposits stretch over 12 kilometres, from the Hugo Dummett North Zone in the north through the adjacent Hugo Dummett South Zone, down to the Oyut Deposit, extending to the Heruga Deposit in the south. While we currently produce all of our concentrate from the open pit, the best minerals, over 80 per cent of Oyu Tolgoi’s total value lies deep underground. It is one of the best copper-gold ore bodies anywhere in the world. We are looking to develop an underground mine complex, using block-caving mining techniques to extract the ore and transport it to the surface to the concentrator.

Block-caving, while technically challenging, is one of the safest and most cost-effective methods of mining ore from deep below the ground. The block caving mining method at Hugo North will make Oyu Tolgoi a long-life, sustainable producer and a major contributor to the world copper market.

Fourteen kilometres of lateral tunnels have already been constructed at Oyu Tolgoi. Over time, up to 200 kilometres of tunnels, at depths of up to 1,300 metres, will be built to allow safe mining of the deepest parts of Oyu Tolgoi’s ore body.

General information on Oyu Tolgoi underground development

Key facts about Oyu Tolgoi underground mine:

  • 80 per cent of Oyu Tolgoi’s value lies beneath the surface
  • Mining method: Block caving
  • Operations: The mine will work 365 days a year with two 12-hour shifts.
  • At the peak of construction, the underground workforce is expected to be over 3,000 – and majority Mongolian.
  • The total conveyor length (10 km) is as long as the distance from the Chinggis Square to Tolgoit station.
  • The deepest shaft is the equivalent of 12 Blue Sky Towers in depth.
  • Total length of tunnels over the life of Hugo North Lift 1 - 200 km (mostly with a height of 5.5m and a width of 5m)

What is block caving?

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.

Learn more about the Oyu Tolgoi Underground Development from this poster.

OT Underground Mine Poster