In this study,by changing both pier diameters and particle sizes of sand bed in flume experiments,the scour process around cylindrical bridge piers under an ice-covered flow condition has been investigated.It is found that the appearance of an ice cover on the water surface caused a deeper and wider scour hole in comparison with that in an open flow with identical flow rates,implying a larger volume of scour hole under an ice-covered flow condition.Similar to the scouring process at a bridge pier under an open flow condition,both the depth and volume of a scour hole increase with the flow velocity and pier diameter.Comparing with results under an open flow condition,for identical flow rates,the maximum depth of a scour hole under an ice-covered flow condition increased by about 20％-30％,and both the scour area and volume of a scour hole increased by about 40％-50％.A flow at Froude number of 0.15 is the demarcation point for assessing an obvious impact of an ice cover on the local scour around a bridge pier in this experimental study.Using data collected from laboratory experiments,equations have been developed to calculate the maximum scour depth,scour area and scour volume.Results of present study have been compared with those of others.
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