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Argyle Diamond Mine is situated in the East Kimberley region of Western Australia. Block-cave mining is ongoing below the mined-out South Bowl pit. Average annual rainfall is about 800 mm. A constant flow of groundwater between 60-100 L/s enters the cave zone laterally from various permeable layers in the surrounding country rock. In addition, ephemeral runoff from the overlying pit rapidly infiltrates into the surface of the cave. In 2014, two major rainfall events occurred: 175 mm falling in 48hrs on 15th-16th January; and 213 mm falling in 72hrs on 6th-8th February. The January 2014 rainfall event caused a short term peak mine inflow of 500 L/s, whilst the February 2014 event caused a peak inflow of 1200 L/s.

A rainfall-runoff-frequency model was created to assess runoff volumes reaching the base of the pit. This was coupled with a numerical flow model developed to assess the passage of water from the pit floor to the mine extraction level. The model incorporated rock mass hydro-geomechanical changes based upon the predicted future Life of Mine cave zone propagation. The coupled model was calibrated to the two major 2014 runoff events. The model was then used to simulate a series of potential future rainfall-runoff events and future underground inflows. The analysis was used to develop a Trigger Action and Reponse Plan (TARP) for the future flood management.

Calibration demonstrated that peak inflows to the mine workings were found to be highly sensitive to the propagation of the caved zone to the pit surface over mine life and prior water content of the cave zone. Current pump capacity and operational alarms were found to be insufficient to deal with extreme inflow events. The model results were used to develop new criteria for activation of seasonal pumps within the mine.

Proceedings IMWA 2016, Freiberg/Germany | Drebenstedt, Carsten, Paul, Michael (eds.) | Mining Meets Water – Conflicts and Solutions
Argyle Diamond Mine, Rio Tinto, Perth
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