State-of-the-Practice Design of Segmental Retaining Walls: NCMA.s Third Edition Manual

The National Concrete Masonry Association (NCMA) published the First Edition of the Design Manual for Segmental Retaining Walls (DMSRW) in 1993 to provide a standardized engineering approach for the analysis and design of conventional and reinforced soil segmental retaining walls (SRWs). The Second Edition of the DMSRW was published in 1997 and the companion NCMA Segmental Retaining Wall Drainage Manual was published in 2002; the latter provided general guidelines for incorporating surface and subsurface drainage details and systems into SRW design and construction to minimize the potential for hydrostatic forces to develop and to provide guidance for including hydrostatic forces when drainage alone will not eliminate the potential for water to load the SRW. The Third Edition of the DMSRW, completed in 2006, incorporates significant changes in the state-of-the-practice regarding MSEW and SRW topics. This paper summarizes these changes and discusses the rational for each. This paper will serve as a useful guide for practioners, particularly those designing with the aid of software based upon the earlier Second Edition of the DMSRW. The paper is directed towards designers and specifiers of the materials and methods used for SRWs.