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    bridge scour

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    Determine the magnitude of the contraction scour depth given the following information about the channel and bridge:

    (a) The upstream channel width = 322-ft; depth = 8.6-ft
    (b) Q = 27,300 ft3/sec
    (c) Channel slope = 0.004-ft/ft
    (c) Bridge abutments consist of vertical walls with wingwalls, width = 122-ft; with three sets of piers consisting of 3 columns 15-inches in diameter
    (e) The bed material size: the D50 = 0.0023-ft with a fall velocity = 0.33-ft/sec
    (f) Original depth at bridge is estimated as 7.1-ft (Ans: ys = 10.1-ft)

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    Solution Preview

    discharge, Q1 = 27300 ft^3/s
    Width, W1 = 322 ft
    Depth, y1 = 8.6 ft
    Area, A1 = W1*y1
    velocity, V1 = Q1/A1 = Q1/(W1*y1) = 27300/(322*8.6) = 9.86 ft/s

    Threshold velocity, Vt = Ku * y1^(1/6) * D50^(1/3)
    D50 = ...

    Solution Summary

    Corresponding to a given channel specifications, scour depth (ys) is estimated.