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Case description

A high-grade underground silver mine was operating below the water table within a karst limestone formation that included numerous faults and other water-bearing structures.

Potential water inflows were controlled by drilling probe holes and injecting cement prior to advancing development and production headings.

While reaming a new ventilation raise, the reamer encountered an un-grouted fracture that resulted in a high volume water inflow of approximately 40,000 USGPM that rapidly flooded the mine workings.

Solution

The mining company contacted Peter White to direct mine recovery operations.

Surface exploration drill rigs were used to drill three holes that intersected locations near the water inflow.

Peter worked with a local ready-mix supplier to formulate a cohesive cement-sand grout mix to fill the mine openings beneath the water inflow location. A conventional concrete pump truck was used to deliver several ready-mix truckloads of cement-sand grout to fill the ventilation raise and associated access tunnel.

Surface holes were then re-drilled to verify site conditions and conventional cement grouting operations were undertaken to seal residual water-bearing fractures.

Within a few days after the mine flood event, crews were able to dewater the mine workings and resume mining operations. After additional probe drilling and grouting work near the inflow location, access to the ventilation raise was reopened and the ventilation raise was successfully constructed.

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