The role of monitoring information in the design of underground powerhouses

The underground powerhouse of the Lubuge Hydroelectric Power Station is 125 m long, 38.4 m high and 18 m wide. It is built in a Triassic formation consisting of limestones, limy dolomites and dolomitic limesstones etc. The surrounding rock of the powerhouse has heen reinforced by rock bolts and thus is rather stable. During the construction of the powerhouse, the deformation of the surrounding rock was monitored. In this paper, the initial stresses in the rockmass before excavation were obtained by back analysis of the deformation data observed in the undrground powerhouse; a failure model which accounts for the elasticity and brittle fracture of the surrounding rock was established by analysing the result of deformation observation, the phenomena in the surrounding rock after excavation and the results of rock mechanics experiments; the stress distribution in the surrounding reek and the reinforcing effects of rock bolts were computed by the FEN and the mechanism of anchorage effects was analysed. The result of the present study suggests that for underground projects carried out under similar conditions iii the future, the cost for anchorage supporting can be further lowered by improving the design.