THE FINAL PIECE OF THE PUZZLE: RE-DESIGN OF GROUTED CLOSURES FOR A DAM CUTOFF WALL

摘要

Buckeye Lake Dam was substantially remediated between 2015 and 2018 as a result of unacceptable damsafety performance. A permanent seepage cutoff, consisting primarily of a soil mixed cutoff wall(SMCW) with occasional sections of steel sheet piling, was constructed along the dam alignment.Closures were required at the terminus of the soil mix elements with existing structures or coffer cells,and at locations where new sheet piling was constructed parallel to the new soil mixed cutoff wall,creating a short circuit seepage path. The original proposed design to construct these closures includedpermeation grouting methods with chemical grouts. However, a combination of multiple chemical grouttypes, multiple grout pipes, and an extensive post-grouting verification program was required to ensurethe design intent was achieved. After award of the project, the specialty grouting contractor elected toevaluate jet grouting as an alternative closure construction method. The advantages of the jet groutingoption offered potential schedule and cost savings to the project as well as a superior product for seepagereduction, given the mixed soil conditions at the site. This paper presents an examination of the siteconditions and project goals for the construction of the proposed closure elements for the rehabilitation ofBuckeye Lake Dam. Descriptions of the original and alternative treatment methods are provided, withexpected performance results. A description of the relative strengths and deficiencies of each method, aswell as the feasibility and constructability of each method is provided. The implementation of the jetgrouting program is presented, including a discussion of the design elements, quality control test methods,movement monitoring, and verification test methods. This paper also examines the risks associated withjet grouting and how those risks were mitigated during the grouting operations.