Managing Liability in the Design and Construction of SRW/RSS Structures

The use of Segmental Retaining Wall (SRW) and Reinforced Soil Slope (RSS) structures are becoming increasingly common for site development projects. The authors have been directly involved with the specification, design, and construction of new structures, and the investigation and litigation of failures of these structures. It is our observation that most failures could have been prevented with proper geotechnical assessment, design coordination and review, and construction oversight and testing. Geotechnical engineers play a key role in the successful implementation of a SRW/RSS project, and may carry liability for the performance of the structure. This liability can be reduced or better controlled if the geotechnical engineer is directly involved in the planning, design and construction of SRW/RSS structures. This paper discusses a number of design issues that are critical to the successful construction of a SRW/RSS structure, including characterization of site subsurface conditions and reinforced backfill, assessment of global stability, and the establishment of proper design criteria. Involvement by the geotechnical engineer during site planning and design is equally important. The project delivery method commonly used on SRW/RSS projects is contractor-led design-build. This often leads to poor communication with design team members and reduces or eliminates the geotechnical engineer's involvement during the design. Construction oversight is needed to verify the wall is constructed properly and testing must be adequate to verify the design assumptions. A qualified engineer must coordinate both the oversight and testing to assure that test results and conditions are properly interpreted. Geotechnical engineers must be more pro-active with clients to ensure the opportunity to adequately investigate site conditions for a SRW/RSS, provide design recommendations or prepare the design themselves, and provide adequate oversight and testing during construction.