Channel Bed Deformation And Ice Jam Evolution Around Bridge Piers

The existence of local scour near the pier will cause a change in the flow state and river level near the pier,which will interact with the evolution of the ice jam near the pier,and the more complex water flow structure in the curved channel makes the local scour and ice jam evolution in the bend different from the straight.Through the straight and curved ice jam tests,the evolution of ice jams and the development of scour pits are compared and analyzed under the conditions of local scouring with and without piers.The findings suggest some differences in the interaction between local scouring of bridge piers in straight and curved channels and the evolution of ice jams.Regardless of the straight,curved channel,under the same hydraulic and ice flow conditions,compared with the local scouring conditions without piers,the time required to complete the initial ice jam stage is relatively shorter.Meanwhile,the equilibrium ice jam body thickness and the equilibrium ice jam water level are more significant,and the time required to achieve ice jam equilibrium is longer.Under similar ice flow conditions,regardless of the straight,curved channel,the Ti/h value of the pier section decreases with the increase of initial water flow Fr of the pier section and increases with the increase of Qi/Qw.Scour pits develop faster under ice jam conditions than under open current conditions.In the straight channel,the regression equation for calculating the depth of scour pits under ice jam is given by considering the factors such as the water depth,flow rate,ice jam thickness,the ratio of ice flow to water flow,the pier shape coefficient and the median particle size of sediment.In the curved channel,the regression equation for calculating the depth of scour pits under ice jam is given by considering the factors such as water depth,flow rate,the ratio of ice flow to water flow,pier diameter and the thickness of ice jam on the convex and concave banks.At the same time,some differences exist in the interaction between the local scouring of bridge piers in the straight and curved channels and the evolution of the ice jam.Under the same hydraulic and ice flow conditions,under the condition of local scour in the straight flume,the equilibrium of ice jam thickness and the equilibrium ice jam water level on both sides of the same cross-section are basically the same as the value-added of the equilibrium ice jam thickness and the equilibrium ice jam water level under the condition of without local scour,and in the curved channel,compared with the concave bank,the value-added of the equilibrium ice jam thickness and the equilibrium ice jam water level on the convex bank is greater.