Tumut 2 Underground Power Plant

The comprehensive program of field exploration, rock tests, photoelastic model studies, and instrumentation carried out for the Tumut 2 Underground Power Plant enabled the design and construction of the underground openings to be completed without the necessity of any significant alterations during the construction period. The plant was sited and orientated from the geological information obtained from an exploratory tunnel and diamond drilling. The properties of the in situ rock mass were obtained from flat-jack and plate-bearing tests that indicated the presence of high horizontal rock stresses. The shape of the main openings, the design of the concrete arch roof supporting the rock in the machine and transformer halls, and the sequence of excavation were determined from photoelastic model studies conducted to predict the change in the pattern of the rock stresses as the excavation of the underground openings proceeded downwards.