| There are very few new dams being built in the U.S., and a major emphasis in earth dam design and construction has been placed recently on the re-evaluation of existing earth dams. Many existing earth dams have been classified as unsafe by modern standards, for both static and dynamic conditions. The emphasis of this study was on the use of advanced analysis techniques for dam rehabilitation. These methodologies were applied to Lyman Dam in Northeastern Arizona.; The ratio of undrained shear strength to the major principal stress at the end of consolidation, before shearing (Su/P) as a function of P for undrained shear strengths, coupled with consolidation modeling, was used to evaluate the shear strength of over-consolidated, clayey soils. This was enhanced by the incorporation of staged construction and wick drains into the time-dependent consolidation model. Embankment design optimization, considering fill volumes, stability, and staged construction including temporary fills was also used.; In addition, pore pressure dissipation predictions based on fill rates were used to anticipate shear strengths needed for stability. Pore pressure monitoring and in-situ testing during construction were used to determine when it was safe to begin the second phase of construction, and to verify the models used for analysis.; These techniques can be used in other rehabilitation projects to avoid the use of over-conservative soil properties which lead to higher costs for construction. |
