Abstract: A bank stability analysis model of underwater riprap revetment is presented that has been adopted to calculate the riprap failure processes at two typical cross sections of Beimenkou in the lower Jingjiang from 08/2017 to 10/2018. The impacts of different factors on revetment collapse are examined, including near-bank velocity, bed erosion and deposition, riprap-rock size, and bank slope. The calculations show that in this period, generally the riprap revetment was relatively stable with an average collapse ratio as low as about 5%. This ratio grew as flow velocity increased, and its growth became sharp at a certain critical velocity value that was higher in the condition of riprap with a larger angle of repose. A similar variation trend also showed between the collapse ratio and bed scour depth. With the increasing riprap-rock size or the decreasing underwater slope, the collapse ratio decreased gradually. Generally, riprap revetment with an underwater slope lower than 1:2.0 showed better stability.

Key words: riprap revetment, bank stability model, collapse ratio, Jingjiang reach, critical value of stability