Construction Implications from Geological Modelling at the Enlarged Cotter Dam site, ACT, Australia

摘要

The Enlarged Cotter Dam (ECD) Project comprises the construction of a new 80m high rollerrncompacted concrete (RCC) water supply dam, located 120m downstream from an existing 31m high,rnconcrete gravity Cotter Dam, 18km west of Canberra, in the ACT, Australia. The dam site is locatedrnin a steeply-sided valley, with overall abutment slopes in the order of 45°, that have been erodedrnthrough a geological sequence of Early to Late Silurian Age, comprised predominantly of porphyriticrnrhyolite and lapilli tuffs of the Walker Volcanics. The geology and topography of the dam siternconstitute a distinctive environment for the construction of the ECD. An understanding of therngeological model of a dam site can inform both design considerations and construction planningrnaspects. This paper focuses on implications for construction that have been identified through arnreview of the site’s geological model. Implications drawn from geological modelling at the ECD siternhave been identified as applicable to the following key construction issues:rn1.Required depth of abutment strippingrn2.Useability of stripped abutment spoilrn3.Foundation excavation stabilityrn4.Forecasting stabilisation types and quantities.