UNSW Geotechnical Centrifuge Supporting Groundwater Management in Perth

Posted 1 August 2015

Operating the centrifuge

By Doug Anderson

The Water Research Laboratory (WRL) of the School of Civil and Environmental Engineering at UNSW Australia has just completed initial centrifuge testing of thirteen drill core samples recovered by Water Corporation from a test hole at Beenyup in Western Australia.

The centrifuge testing was commissioned by Western Australia's Department of Water to better inform the Perth Confined Aquifer Capacity Study. This study aims to improve the understanding of the Leederville and Yarragadee aquifers that are central to the security of Perth's potable water supply. UNSW Australia's unique centrifuge facility provided government hydrogeologists with point scale measures of vertical hydraulic conductivity for sandstone and shale samples in the range of 1 x 10⁻⁶ to 1 x 10⁻¹² m/s.

Results from WRL's centrifuge testing will now be up-scaled to constrain and better inform conceptual and numerical models of vertical groundwater flow in the Beenyup area. This will in turn support assessments of where Managed Aquifer Recharge (MAR) can best beused as a groundwater management strategy for the position of the seawater interface and for the protection of overlying groundwater dependent ecosystems. This is particularly important in Perth as pumping from all aquifers contributes more than 50% of the total water supply.

The centrifuge facility at WRL (pictured below) allows engineers and scientists to force water or other solutions through drill core using body forces of up to 500 times normal gravity.For this project, this enabled the measurement of permeability in tight material within hours or days that would have otherwise taken weeks or months to complete. Hydraulic conductivity was calculated using a modification of Darcy's Law for constant and falling head tests that accounted for centrifugal forces.

Data-sets from the facility inform best-practice design for a wide range of engineering projects where an understanding of vertical leakage, aquifer connectivity or contaminant transport is important. The centrifuge facility at WRL has applications for the design of clay liners, managed aquifer recharge, mining and coal seam gas activity. The centrifuge can also be used to examine the geochemical interactions of different waters within many tight porous materials.

The centrifuge facility installation has been funded by the National Water Commission, the National Centre of Groundwater Research and Training (NCGRT) and is managed by the UNSW Connected Waters Initiative (CWI) with support from the School of Mining Engineering and the School of Civil and Environmental Engineering.

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