Treatment of Main Geological Defects during Excavation Construction of Wudongde Underground Powerhouse Caverns

Underground powerhouse is adopted by Wudongde hydropower plant on both left and right bank. The excavation scale of the main powerhouse is 333.0×32.5×89.8m (length×width×height ) that ranks top on the world. The underground powerhouse caverns are hosted in the fold basement of the Presinian system that belongs to the layered epimetamorphic rock. Geological condition is complicated and rock stratum is steep towards the downstream and characterizes in "thin, hard and crisp". During excavation construction of the underground powerhouse, geological defects such as small angle between surfaces, B type breccia, carbon film attached on surface, blocks, large and long discontinuities with small angle are exposed. The targeted treatments for the geological defects are proposed and implemented based on numerical feedback analysis and references of similar finished projects. Excavation and supports of the main powerhouse are all constructed completely at present and monitoring displacements tend to be convergent. The proposed treatments are verified to be reasonable and effective and provide reference for subsequent similar projects.