Bi-Directional Load Testing of Shafts to 6000 Tons

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by Jeffrey W. Goodwin, LOADTEST Inc, Gainesville, United States,

Document Type: Proceeding Paper

Part of: Design and Performance of Deep Foundations: Piles and Piers in Soil and Soft Rock

Abstract: This paper describes the use of Osterberg cells (O-cells) to perform bi-directional load testing on full size production drilled shafts for a major bridge foundation near Owensboro, Kentucky. Two fully instrumented, 1.83 m (72in.) diameter drilled shafts were constructed with rock sockets in soft sandy shale, with the top of shaft 17 m (57 ft) below the surface of the Ohio River. Even though a surface reaction system was not used, the O-cell loading at the base of the shaft permitted application of a combined shear and end bearing load of 53 MN (6000 tons) without failure occurring in either component. This method enabled the testing of full size production shafts beyond their required design ultimate load capacity at a site where full scale conventional static testing would have been impractical. Results from one of the load tests are compared with recently developed design methods for estimating unit shear resistance in intermediate geomaterials. To determine if the correlations based on the laboratory testing results provided appropriate design criteria for the large diameter shafts.

Subject Headings: Load tests | Shafts | Bridge foundations | Load factors | Load bearing capacity | Bridge tests | Failure loads | Failure analysis | Ultimate loads | North America | United States | Ohio River | Minnesota | Kentucky

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