ALTERNATIVES TO RIPRAP AS A SCOUR COUNTERMEASURE

Riprap is the most common and best documented method of protection against local scour at bridge piers. Alternatives to riprap vary in size, shape, and mass as well as flexibility of design. The overall performance of alternatives such as grout mats and grout bags, extended footings, tetrapods, cable-tied blocks, anchors (used in connection with countermeasures) and high-density particles is evaluated. In general, alternatives are used when riprap is hard to obtain, the size required for high-velocity streams is unreasonable, or riprap is difficult to place, among other reasons. Various tests were performed on all previously mentioned countermeasures with and without a pier on a fixed bed. An obstructed movable-bed condition was also tested to obtain qualitative data for each countermeasure. Recommendations for implementing these alternatives are based on laboratory results and include the effects of filter fabric, lateral extent of the countermeasure, sealing between the face of the pier and the countermeasure, and anchoring. The impact of the drag coefficients on the stability of the countermeasure was also examined. The results of these experiments provide some comparative conclusions among the countermeasures as well as criteria for the design and implementation of these devices in the field. Investigations at an FHWA hydraulics laboratory over several years are summarized, including results of the investigations of riprap and of alternatives to riprap. As a local scour countermeasure, each alternative has its unique attributes that, depending on the application, may provide superior protection over riprap.

Language

  • English

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: p. 261-278
  • Monograph Title: FOURTH INTERNATIONAL BRIDGE ENGINEERING CONFERENCE, SAN FRANCISCO, CALIFORNIA, AUGUST 28-30, 1995. CONFERENCE PROCEEDINGS, 2 VOLUMES
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00711732
  • Record Type: Publication
  • ISBN: 0309061091
  • Files: TRIS, TRB
  • Created Date: Sep 6 1995 12:00AM