Author(s): Yun Li; Huojian Liu; Xiaogang Wang; Guoxiang Xuan; Andre Rene Koelewijn
Keywords: Downstream slope of dam; Shear stress; Overtopping; Numerical simulation
Abstract: Under the condition of exceeding standard flood, water shear stress on downstream slope of dam due to overtopping is the direct force which causes dam failure. It’s a great significant for the mechanism of dam breach to know its distribution law. Using k-ε turbulence model to close Reynolds time-averaged equation and volume of fluid method to track free face, a 2D numeral model was established. It was proved it was valid through comparison between simulation results and experiments results. A detailed research of shear stress on downstream slope of dam was conducted under the condition of different overtopping depth, dam slope and dam height. According to dimensional analysis the water shear stress is relate to overtopping water depth h, dam height H, gravitational acceleration g, water density ρ, relative position (the ratio value between the horizontal distance from dam surface points to dam abutment and dam height) and so on. Based on the simulation results a unified computing formula is founded which can calculate water shear stress at any location of downstream slope of dam with different overtopping depths, dam slope and height (while dam height is from 6m to 12m, slope from 1: 2 (H: V) to 1: 3 (H: V) and overtopping water depth（while overtopping water depth is from 0. 2m to 1m）. It covers the largest proportion of small and medium-sized earth-rock dam in China. Comparison of the formula’s and numerical simulation’s results shows the formula has a good prediction accuracy. It’s significant to understand the process of breach formation, mechanism of dam breach and to guide dam protection under the condition of exceeding standard flood.