Effects of hooked-collar on the local scour around a lenticular bridge pier |
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| Institution: | 1. Department of Civil Engineering, International Islamic University, Islamabad 44000, Pakistan;2. Department of Civil Engineering, Lakehead University, Thunder Bay, ON P7B 5E1, Canada;3. College of Engineering and Science, Victoria University, P.O. Box 14428, Melbourne, VIC 8001, Australia;4. Department of Civil Engineering, University of Engineering and Technology, Taxila 47080, Pakistan;5. James Watt School of Engineering, University of Glasgow, Glasgow G12 8QQ, United Kingdom |
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| Abstract: | This paper presents the results of comprehensive laboratory experiments to investigate the effects of hooked-collar on the scour development around a vertical pier with a lenticular cross section. The flow around the pier was uniform, steady, and under the clear-water condition. The axial scour profiles for cases without and with a lenticular hooked-collar were measured and the effects of hooked-collar dimensions and elevation from the bed were examined. To compute the efficiency of hooked-collar for scour prevention, the results of local scour for a bridge pier without a collar and a bridge pier with a plain collar, without a hooked wall, were used as benchmark data sets. A wide range of hooked-collar geometries such as the ratio of collar width to the pier width, Wc/Wp, ranging from 1.5 to 3.5, the ratio of hooked-collar wall height to the pier width, Hc/Wp, ranging from 0.15 to 0.6, and the ratio of collar elevation to the pier width, Ec/Wp, of ?0.5, 0, and 0.5 were tested. The experimental results indicated that the equilibrium scour depth decreased with the ratio of hooked-collar to the pier width when Wc is twice the pier width, Wp. For Wc/Wp > 2, the scour depth was similar to the tests with an infinitely large pier width. In addition, the scour depth consistently reduced as the hooked-collar wall height, Hc, to the pier width, Wp, approached 0.3. The highest scour reduction efficiency was achieved when the hooked-collar being placed on the bed surface. Empirical models were developed for prediction of maximum scour depth near the lenticular bridge pier with a modified collar. The results showed that the volume of scour hole around a lenticular pier increased non-linearly with the maximum scour depth and it was independent of the hooked-collar geometry. |
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| Keywords: | Local scour Erosion Collar Hooked-collar Lenticular pier Scour countermeasure Steady flow |
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