'Unconventional' drilling could free trapped Chilean miners

An ‘unconventional’ drilling method is expected to bore the escape hole for the 33 miners trapped in a San Jose copper mine in northern Chile, according to an industry expert.

Dr Andrew Wetherelt, a senior lecturer in mining engineering at the University of Exeter, said Chile’s state-owned Codelco mining company is planning on using a massive Strata 950 ‘raise boring’ drill to carve a hole 66cm wide to reach the miners trapped under solid rock 700m below the surface.

This hole will be drilled after the rescue team has completed drilling a smaller pilot hole.

In traditional raise boring operations, Wetherelt said mining companies use a drilling technique known as ‘up-reaming’ where machine cutters are fitted to the drill sticking out the bottom of the pilot hole. The massive cutters are raised up as they hack their way through thick rock.

Wetherelt said this is not possible to do in the case of the mine in Copiapo, Chile because the collapsed mine offers no access to the bottom.