Abstract: To investigate the effect of discharge through surface outlets and bottom outlets simultaneously, we analyze the uplift force and its distribution on plunge pool slab through a 1∶50 model test. Large water rolls formed by the nappes from surface outlets and bottom outlets interact with each other, and thereby weakening the entrainment effect on the slab. As a result, the uplift force near the impact point of water nappe by coalition discharge from surface outlets and bottom outlets is obviously smaller than that by separate discharge from surface outlets or bottom outlets alone. In the case of coalition discharge, the location of maximum uplift force also changes, moving forward near bottom outlets and moving backward near surface outlets. 

Key words: water conservancy and hydropower engineering, uplift force, coalition discharge, hydraulic model, high arch dam