Shaft construction associated with a mine expansion project was stopped when 1,200 GPM of water inflows were encountered within an aquifer zone at a depth of 43 meters below the 250 meter level at underground silver mine.
The mining company contacted Peter White to provide engineering direction to overcome the water inflow, supply specialized grouting equipment and accessories, as well as to provide on-site training for company crews to undertake the required drilling and grouting work.
To overcome the water inflow situation, Peter designed a systematic drilling and cement grouting program using long diamond drill holes collared from the underground 250 level that extended to the planned bottom of the mine shaft for a cement grouting operation to minimize water inflows for future shaft sinking, associated level development and loading pocket construction.
The grouting program involved cement grouting to reduce high volume water inflows through fractured rock and water-bearing ground conditions. Regular Portland cement was mixed at a W:C ratio of 2 by weight of cement, as thicker grout mixtures would not penetrate the water-bearing aquifer formation.
Cement grouting equipment supplied by Peter included a double-drum grout mixer and high-pressure plunger pump rated for the volumes and pressures required to undertake the project, as well as an electromagnetic grouting flowmeter, in-line diaphragm pressure sensors and liquid-filled pressure gauges.
Initial reductions in water inflow rates were observed after completing primary hole drilling and grouting operations. Subsequent secondary and tertiary holes were drilled and grouted to close in the spacing between adjacent drill holes, resulting in the successful overall reduction of water inflows that enabled resumption of shaft sinking activities.