分析了表孔及中孔挑流水舌上下碰撞能量损失、 3 -D扩散和漏碰等水力特点 ,用动量方程和水舌空中扩散宽度沿程变化规律导出 3 - D碰撞流速、碰撞效率和碰撞能量损失 ,得出碰撞最佳水力条件。分析碰撞水舌对基岩冲刷特点 ,提出表、中孔水舌上下碰撞作用下基岩冲刷平衡深度估算方法。小湾表孔、中孔碰撞工况下基岩冲刷试验表明 ,预报值和试验值在各级库水位下基本吻合。研究表明预报方法可行的 The hydraulic characteristics such as energy loss, 3-D diffusion and leakage were analyzed. The relationship between 3 - D collision velocity, collision efficiency and collision were derived by using the momentum equation and the variation law of air diffusion width along the water tongue. Energy loss, come to the collision of the best hydraulic conditions. The erosion characteristics of collision water tongue on bedrock are analyzed. A method for estimating the erosion depth of bedrock under the collision of upper and lower hollow water tongue is proposed. The test results of bedrock scouring in Xiaowan surface and medium-hole collisions show that the predicted value and the test value are in good agreement with the reservoir water level at all levels. Research shows that the forecasting method is feasible