Abutment Seepage at Smithville Dam

by Francke C. Walberg, US Army Corps of Engineers, Dams, & Foundation Section, Kansas, City, KS, USA,
Heidi L. Facklam, US Army Corps of Engineers, Dams, & Foundation Section, Kansas, City, KS, USA,
Karl D. Willig, US Army Corps of Engineers, Dams, & Foundation Section, Kansas, City, KS, USA,
John E. Moylan, US Army Corps of Engineers, Dams, & Foundation Section, Kansas, City, KS, USA,



Document Type: Proceeding Paper

Part of: Seepage and Leakage from Dams and Impoundments

Abstract: After initial filling there was concern for the stability of Smithville Dam when higher than anticipated piezometric levels were experienced in the left abutment foundation. Concern heightened when review of strength data led to uncertainty about design shear strengths for foundation shales. An investigation consisting of exploratory drilling, sampling, testing and instrument installation was undertaken to determine the subsurface conditions (including the shale shear strength), to re-evaluate the stability of the dam and to monitor the left abutment area. The investigation revealed a continuous basal zone of coarse, glacial outwash sediments which is transmitting high piezometric pressures through the abutment. Shear strength of the shale was about the same as for design. A stability analysis showed that pressure relief wells at the downstream toe and under the downstream slope would provide a satisfactory safety factor.

Subject Headings: Shear strength | Dam foundations | Shale | Soil surveys | Foundation design | Subsurface investigation | Dams | Overwash

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