Local scour around a bridge pier under ice-jammed flow condition - an experimental study

• Published in: Journal of Hydrology and Hydromechanics
• Main Authors: Wang, Jun, Hou, Zhixing, Sun, Hongjian, Fang, Bihe, Sui, Jueyi, Karney, Bryan
• Language: English
• Subjects: ice jam; ice cover; riverbed deformation; local scour; bridge pier; Ice Sheet
• Online Access: https://kramerius.lib.cas.cz/view/uuid:1b7cafe6-904b-490c-a100-98948b972e29; https://doi.org/10.2478/johh-2021-0014

The appearance of an ice jam in a river crucially distorts local hydrodynamic conditions including water level, flow velocity, riverbed form and local scour processes. Laboratory experiments are used for the first time here to study ice-induced scour processes near a bridge pier. Results show that with an ice sheet cover the scour hole depth around a bridge is increased by about 10% compared to under equivalent open flow conditions. More dramatically, ice-jammed flows induce both greater scour depths and scour variability, with the maximum scour depth under an ice-jammed flow as much as 200% greater than under equivalent open flow conditions. Under an ice-jammed condition, both the maximum depth and length of scour holes around a bridge pier increase with the flow velocity while the maximum scour hole depth increases with ice-jam thickness. Also, quite naturally, the height of the resulting deposition dune downstream of a scour hole responds to flow velocity and ice jam thickness. Using the laboratory data under ice-jammed conditions, predictive relationships are derived between the flow’s Froude number and both the dimensionless maximum scour depth and the dimensionless maximum scour length.