Prediction and Control of Downpull on Tunnel Gates

Abstract

A one‐dimensional analysis of the discharge passing under a tunnel gate and of the hydraulic downpull acting on it is presented. It is shown that the downpull is significantly affected not only by the geometry of the gate bottom, but also by the rate of flow passing over the top of the gate through the gate well. In fact, the downpull on a tunnel gate of a given form can be significantly reduced by appropriately controlling this overflow. To facilitate prediction of possble negative downpull, which might inhibit safe gate closure, the analysis is expanded to include the dangerous range of extremely large gate openings and the unsteady effect of gate movement. Data on all the significant flow and downpull parameters are given as obtained from systematic watertunnel experiments. In conjunction with these data, the analysis should prove useful as a design tool.