How To Dewater The Site Of A New Mine
Dewatering a mine involves using various techniques to either intercept groundwater before it infiltrates the mine or to collect it and remove it from the mine after it has entered.
Pore Water Pressure Reduction
Pore water pressure refers to the groundwater pressure held within the soil in the gaps between particles. High pore water pressure can destabilise underground openings and slopes. Dewatering can reduce pressure and improve stability.
Groundwater Control By Pumping
This dewatering procedure involves pumping groundwater from wells or sumps located around the mining site. This temporarily lowers groundwater levels and enables excavations to be carried out while conditions are dry and stable.
In its simplest form, groundwater pumping is achieved through sump pumping, whereby groundwater is allowed to enter the excavation site before being collected by a sump and pumped away. Sump pumping is useful in some conditions but allowing water to seep into the excavation site can decrease stability.
Groundwater Control By Exclusion
Exclusion involves the creation of an impermeable barrier which prevents groundwater from entering the excavation site. This approach is best suited for situations where it is desirable to minimise the amount of pumping required, such as when other site dewatering methods that lower groundwater might affect nearby structures.
Open-pit dewatering uses pumps to pull water from the bottom of the excavation area. This method needs to be combined with other site dewatering methods to lower the groundwater table outside the pit and prevent groundwater from filling the pit back up again.
Deep Wells Pumped By Submersible Pumps
Electric or diesel motors can be used to power hydraulic submersible pumps. Diesel is preferred for mining sites without a reliable source of electrical power. Submersible pumps can be lowered into the pit to remove standing water.
Atlantic Pumps's submersible pumps are ideal for this purpose with seal failure devices that protect the pumps from motor failure. They also utilise high-quality strainers to ensure maximum efficiency.
Where To Send Pumped Water
Proper disposal of water pumped by dewatering systems is essential. The viable water disposal options will depend on the local terrain and environmental regulations. Depending on the scenario, water can be disposed of into sewer systems, surface water systems like rivers and lakes, or back to groundwater via recharge wells and trenches.
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