Abstract: The effect of sharp-edge inlet and curved inlet on the discharge capacity and flow regime of steep tunnel is researched by using hydraulic calculation analysis and model test verification. The long steep diversion tunnel of a hydropower project is taken as the research object. Research shows that curved inlet could increase the discharge capacity and reduce the cofferdam height,but brings about free-surface-pressure flow in the tunnel,which is harmful to the safety of tunnel structure; whereas sharp-edge inlet reduces the discharge capacity,but avoids free-surface-pressure flow. Therefore,when the cofferdam scale of hydropower project is small,the sharp-edge inlet is recommended.

Key words: steep slope tunnel, inlet type, hydraulic calculation, model test verification