Engineers Australia

Dams in the Darling Range

Bruce Bulley, Bob Wark and Michael Somerford

Abstract

Geotechnical factors play a major role in the design and construction of dams in the Darling Range east of Perth. These factors are described in relation to case histories for a number of water supply dams that have been constructed over the last one hundred years.

The Darling Range is underlain by the Archaean Yilgarn Craton, which consists of granitic and gneissic rocks that have been intruded in places by dolerites. Conglomerates of suspected Tertiary age occur at North Dandalup and Harvey Dams. The variable weathering in the granitic terrain requires special foundation and permeability control measures. In addition, weathering and ground water movements related to faults, shear zones and contacts contribute to adverse geotechnical conditions commonly found in the Darling Range. The effects of jointing, in particular the pervasive sheet joints, and the presence of corestones in foundation and cut-off excavations, are also described. Problems associated with natural construction materials used for dams in the Darling Range are outlined.