Note: This report provides application of the research summarized in WA-RD 522.1, which has been superseded by WA-RD 522.2, and design procedures based on that research. Therefore, the design procedures provided in this report have been superseded. For the most current design procedures, please see the most recent version of the WSDOT Geotechnical Design Manual. This new design methodology for estimating reinforcement loads in reinforced soil walls, updated in WA-RD 522.2, is termed the K-Stiffness Method (note that the method title “K sub 0 Stiffness Method” has also been superseded by the method title “K-Stiffness Method”).
Description of Superseded Report: This new method has been demonstrated to more accurately estimate reinforcement loads and strains in reinforced soil walls than do current design methodologies. Step-by-step procedures are provided to lead the designer through the reinforced soil wall internal stability design process using this new methodology. These step-by-step design procedures have been developed with a limit states design approach consistent with current design codes (in North America this is termed Load and Resistance Factor Design, or LRFD). Specifically, consideration has been given to strength and serviceability limit states. Load and resistance factors, based on statistical data where feasible, have been developed for use with this method.
The results of examples from actual wall case histories were summarized and analyzed to assess how well the new methodology performs relative to current design practice. From this analysis of the design examples, the following was observed: for geosynthetic walls, the K sub 0 Stiffness Method has the potential to reduce required backfill reinforcement capacity relative to current design methodology by a factor of 1.2 to 3; and for steel reinforced soil walls, the reduction in reinforcement capacity relative to what is required by current design methodology is more modest, on the order of 1.0 to 2.1. Given these findings, use of the K sub 0 Stiffness Method can result in substantial cost savings, especially for geosynthetic walls, because of reduced reinforcement needs.