Construction diversion tunnel design of Goupitan hydropower station

The Goupitan hydropower station is the largest one on the Wujiang rive r. Retaining cofferdams and diversion tunnels are used for the construction dive rsion of the station. There are three diversion tunnels, with two tunnels arrang ed on the left bank and the other one on the right bank. Each diversion tunnelh as a horseshore-shaped flow section of 15.6 m×17.7 m. The geologic conditions for these diversion tunnels of the station are complicated. There exist numerous karst systems and every diversion tunnel has to pass through the Hanjiadian softrock section 100-odd meters long. The design and construction of large-diameter diversion tunnels in such complicated geologic conditions call for high requir ements of design thought and technology. This paper presents the design and cons truction of these diversion tunnels.