Remedial Design of An Earth Dam - 20 Years later

This paper is a sequel to an earlier paper presented by the authors at the 1992 Stability and Performance of Slopes and Embankments-II Conference. The original paper described the failure of the upstream slope of a 13.7 m (45 ft) high earth dam in eastern Ohio. The dam was constructed in 1983 and 1984 and the upstream slope failed upon completion of construction, prior to first filling. Subsurface explorations and monitoring identified the failure surface and revealed that the upstream slope continued to creep. A remedial design was developed that included an earthen berm to buttress the upstream slope. The analyses for the design of the stabilizing berm included laboratory creep tests to establish the appropriate level of stress to include for the portion of the failure surface that remained in place. A stress level was selected with the goal of little or no creep movement during operation. The earthen berm was constructed in 1988 and the reservoir was filled. Performance monitoring includes inclinometer data that show that creep movements continued to occur at a decreasing rate over a 20-year period. This paper describes the post construction creep movements and relates the embankment performance to the testing and analyses completed for the remedial design. A finite element model of the post construction creep movement is developed, using the Plaxis 2D program, to relate the performance data to the design.