In Situ Testing Performed at Jackson Lake Dam

by Jeffrey A. Farrar, Bureau of Reclamation, Denver, United States,
Michael G. Stevens, Bureau of Reclamation, Denver, United States,

Document Type: Proceeding Paper

Part of: Geotechnical Practice in Dam Rehabilitation


Jackson Lake Dam was rehabilitated from 1986 to 1988 to increase seismic stability. Final foundation improvements consisted of dynamic compaction and mixed inplace soil cement columns. This paper presents results of insitu testing performed to evaluate effectiveness of dynamic compaction and a test section of compaction piles. The standard penetration test (SPT) was the primary method for evaluating improvement in terms of liquefaction resistance. Over 4,000 SPT's were performed to evaluate dynamic compaction. SPT data were evaluated by direct comparison of adjacent holes and later with statistical analysis. Results of statistical analysis indicated the importance of drilling method, energy delivery, and correction for particle size. Shear wave velocity was also frequently determined. Crosshole shear wave and spectral analysis of surface wave were compared. Cone penetration testing played a key role in delineating major stratigraphic features during investigations but was used less frequently during ground improvement. Efforts were made to measure changes in insitu stress from compaction piles and dynamic compaction. Tests such as flat plate dilatometer, self-boring pressuremeter, stress captors, stepped blade, conductivity probe, and formation factor probe tests were performed. Application and interpretation of insitu testing was difficult due to complex stratigraphy and the presence of gravels. Recommendations for future applications are given.

Subject Headings: Shear waves | Penetration tests | Field tests | Surface waves | Wave velocity | Soil cement | Seismic tests

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