David Lees provided expertise to the mine in the design and implementation of grouting programs to combat water ingress into the decline development of up to 20 litres/second.
The Blakefield South mine is a completely new underground longwall operation for Xstrata that will replace the production from the Beltana mine from 2010.Walter Mining secured the development of the Blakefield South drift driveage contract progressed the excavation using a roadheader with a fully integrated temporary roof support system for the contract.The access decline is 6m wide and 4.7m high at a grade of 1 in 8 to the North West. The strata is dipping at about 2 degrees due South. At about 120 m from the start of the rock excavation water was intersected in the footwall which flooded the face and made the spoil difficult to remove.
David Lees provided expertise to the contractor to combat the water including design of grouting and dewatering proposals. It was considered that the water and gas were emanating from the Red Bank coal seam about 3m below the tunnel excavation. The Red Bank coal seam is about 6m thick with a suggested confined aquifer of about 50ML. The decline transversed the coal seam over a length of about 40m.
Further, on development of the conveyor drift, significant water inflows occurred at the intersection with a change in grade in the strata. The joint structure associated with this monocline appeared to intercept a large surface water deposit causing water ingress into the drift at over 15 litres/second. David Lees was appointed by the mine to review injection proposals using polyurethane foams and to propose longterm stability solutions for future mine development.
