不同沟床坡度堰塞坝溃口下切过程试验研究

为了解堆积于不同坡度沟床上的堰塞坝溃口下切过程,开展了7组不同沟床坡度(7°,8°,9°,10°,11°,12°,13°)的水槽试验。试验结果表明:堆积于不同坡度沟床上的堰塞坝在漫顶溢流破坏模式下具有相似的溃口下切过程,具体可分为3个阶段,即溃口贯通阶段、加速侵蚀阶段、减速侵蚀阶段。不同沟床坡度条件在一定程度上影响溃决的加速侵蚀阶段,当沟床坡度≥9°时,加速侵蚀阶段以下切侵蚀为主、溯源侵蚀为辅的特征现象被削弱;溃决历时与沟床坡度呈非单调关系,随沟床坡度的增加呈现出先减少后增加的变化趋势;平均下切侵蚀和溯源侵蚀率与沟床坡度呈非单调关系,随沟床坡度的增加呈现出先增加后减小的变化趋势。沟床坡度缓于11°时,溃决历时对沟床坡度的敏感性高于坝前库容;沟床坡度陡于11°时,溃决历时对沟床坡度的敏感性低于坝前库容。

Experimental Research on Longitudinal Breaching of Landslide Dam under Different Bed Slopings

Flume experiment with varied bed slope gradients (7°, 8°, 9°, 10°, 11°, 12°, 13°) was conducted to explore the downcutting erosion of landslide dam breach. Test results demonstrated that despite different slope gradients, the downcutting erosion of landslide dam breach under overtopping failure mode can be divided into three stages: breach penetration stage, accelerated erosion stage, and decelerated erosion stage. The slope gradient of trench bed affects the accelerated erosion stage. When the bed slope gradient is greater than or equal to 9°, the dominance of downcutting erosion supplemented by retrogressive erosion is weakened. Moreover, the duration of breaching is in a non-monotonic relation with slope gradient, shortens at first but then elongates along with the expansion of slope gradient. Average downcutting erosion rate and retrogressive erosion rate are also in non-monotonic relation with slope gradient, rises at first but then declines with the increase of slope gradient. When the slope gradient is smaller than 11°, the sensitivity of duration to slope gradient is higher than that to reservoir capacity in front of the dam; and vice versa.