Design and optimization of flood and sediment releasing tunnel of Shenxigou Hydropower Station

The Diversion tunnel of Shenxigou Hydropower Station is reconstructed for flood and sediment releasing.It was used as diversion tunnel in construction period,and later its outlet was reconstructed as permanent flood and sediment releasing tunnel for bearing 35%-40% of the flood discharge in the operation period.Based on engineering practice of Shenxigou Hydropower Station,we describe layout design of flood and sediment releasing tunnel,flood discharge capacity check,design of energy dissipation and erosion control as well as design optimization.The operation status of flood and sediment releasing tunnel shows that the design scheme is reasonable,which solves the problems of large seepage of chamber,anti-scouring of tunnel floor and energy dissipation and scouring control of the tunnel outlet.