Abstract: To meet the requirements of shipping and economic development, a second shiplock is planned to be built at Dayuandu Navigation-Hydropower Junction, but the approach channel’s entrance area in the upstream of the existing first shiplock is in bend reach with complex flow conditions. To make sure that the flow condition at the second shiplock could meet standard requirements, we designed three cases of cut-off wall pattern, and analyzed the navigation condition, flood discharge capacity and improvement measures under maximum flow (Q=17 500 m³/s, once in 10 years) respectively in the presence of these three cut-off walls.　According to calculation results and comprehensive considerations, we recommend permeable cut-off wall at upstream entrance area of approach channel. The research result could be regarded as reference for similar engineering design.

Key words: Dayuandu hydropower junction, approach channel, permeable, cut-off wall, flow condition, flood discharge