Channel Scour Protection at Roadway Crossingsby Lan-Yin Li Weber, (M.ASCE),
Abstract: There are several forms of channel scour which may damage a bridge or culvert crossing over a natural or improved channel. Typical forms of scour include general degradation, local scour caused by structures, and contraction scour due to encroachment by abutments and roadway approaches. Federal Highway Administration (FHWA) published HEC-18 as a guideline for predicting scour depths at bridge piers and abutments. There are, however, cases to which the application of HEC-18 is not applicable or practical. Although each scour form can be predicted independently using the equations included in HEC-18 but the overall scour may not be the direct sum of all the scour depth. The scour depth can be further complicated by floodplain characteristics, man's activities adjacent to the crossings and the nature characteristics of the channel such as bed and bank materials, geological control and river meandering. Protection of a pipe or box culvert crossing is in principal the same as those shown in HEC-18 for bridges but the erosion control design requirements and procedures have not been well documented. This paper provides a review of the current engineering practices and design methods for channel scour protection at street and highway crossings. Limitations on application of HEC-18 and its supplemental documents are discussed. Future modifications are proposed to promote design efficiency.
Subject Headings: Scour | Bridge abutments | Bridge design | Culverts | Highways and roads | Federal government | Bed materials | Highway and road design
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