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Local and Contraction Scour at Bridge Abutments
In most experimental studies on erosion at bridge piers and abutments, the value of the blockage ratio b/B between the transversal obstacle dimension and the flume width is kept as small as possible (typically b/B < 0.1) in order to avoid constriction and wall effects on the phenomenon. In many practical situations, though, b is not small compared to B so that the average acceleration due to contraction is expected to increase the scour effects of the local acceleration around the obstacle. Standard technical procedures propose to evaluate constriction and local scour depths separately and to sum up the two values, but no data are available to validate the correctness of such an assumption. In this work we present the results of several long duration (1.5→6 weeks) clear water scour laboratory tests around bridge abutments; the time evolution of the erosion process is analysed with respect to local and global characteristic values (maxima, volumes, hole shape). A series of experiments where all the main non-dimensional control parameters other than b/B are kept constant allows to enhance the effect of the constriction ratio alone. Results show that if standard models are used to evaluate contraction erosion, the simple addition of contraction and local effects may lead to a significant overestimation of the total scour.
Local and Contraction Scour at Bridge Abutments
In most experimental studies on erosion at bridge piers and abutments, the value of the blockage ratio b/B between the transversal obstacle dimension and the flume width is kept as small as possible (typically b/B < 0.1) in order to avoid constriction and wall effects on the phenomenon. In many practical situations, though, b is not small compared to B so that the average acceleration due to contraction is expected to increase the scour effects of the local acceleration around the obstacle. Standard technical procedures propose to evaluate constriction and local scour depths separately and to sum up the two values, but no data are available to validate the correctness of such an assumption. In this work we present the results of several long duration (1.5→6 weeks) clear water scour laboratory tests around bridge abutments; the time evolution of the erosion process is analysed with respect to local and global characteristic values (maxima, volumes, hole shape). A series of experiments where all the main non-dimensional control parameters other than b/B are kept constant allows to enhance the effect of the constriction ratio alone. Results show that if standard models are used to evaluate contraction erosion, the simple addition of contraction and local effects may lead to a significant overestimation of the total scour.
Local and Contraction Scour at Bridge Abutments
Ballio, Francesco (author)
Joint Conference on Water Resource Engineering and Water Resources Planning and Management 2000 ; 2000 ; Minneapolis, Minnesota, United States
Building Partnerships ; 1-9
2000-09-11
Conference paper
Electronic Resource
English
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