Advanced Methodology to Assess Riprap Rock Stability At Bridge Piers and Abutments

CHAPTER 2. LITERATURE REVIEW

Riprap is one of the most common countermeasures for bridge scour. For abutments, riprap can be used for design of new bridges and for scour remediation at existing bridges. FHWA does not recommended riprap for the design of new piers, but it may be used for scour remediation issues involving piers. Most reports and guidelines focus on design equations for sizing the rock size for the riprap countermeasure. However, sizing the armor is only one component of the comprehensive design, installation, inspection, and maintenance process required for successful pier or abutment scour countermeasures. Riprap countermeasures are integrated with the structural elements they are designed to protect and, therefore, must include consideration of the armor layer thickness, the filter layer, and apron termination details. Successful performance depends on the response of each component of the system to hydraulic and environmental stresses throughout its service life. All of the following are necessary: filter requirements; material and testing specifications; construction and installation guidelines; and inspection and quality control procedures.

The literature review concentrates on available information, data, studies, and guidelines for riprap failure Modes and design recommendations including significant studies completed through the National Cooperative Highway Research Program (NCHRP). Five comprehensive source documents were identified:

• NCHRP Report 568, Riprap Design Criteria, Recommended Specifications, and Quality Control.⁽²⁾
  
  
• NCHRP Report 593, Countermeasures to Protect Bridge Piers from Scour.⁽⁵⁾
  
  
• Hydraulic Engineering Circular (HEC) 23, Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design Guidelines, Third Edition.⁽¹⁾
  
  
• Melville and Coleman’s reference book, Bridge Scour.⁽⁶⁾
  
  
• Center for Civil Engineering Research and Codes (CUR), Manual on the Use of Rock in Hydraulic Engineering.⁽⁷⁾

Appendix A contains the annotated bibliography developed for this study. Additional sources included bridge scour related papers and abstracts published in the American Society of Civil Engineers (ASCE) Compendium of Papers from ASCE Water Resources Engineering Conferences from 1991 to 1998.⁽⁸⁾ This Compendium contains 371 abstracts and 75 full papers, including a section dedicated to countermeasures.