Drilled Shaft Friction Evaluation via Pullout Tests

by F. C. Townsend, Univ of Florida, Gainesville, United States,
Craig E. Dunkelberger, Univ of Florida, Gainesville, United States,
D. Bloomquist, Univ of Florida, Gainesville, United States,



Document Type: Proceeding Paper

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

Abstract:

The history, development, and field test results of a small-scale 'pullout' test to assess the skin friction (f_su) for drilled shafts socketed in soft rock are presented. Comparisons are made between design f_su values based upon (a) laboratory unconfined compression (q_u), and split tensile test (p_t) correlations, (b) pullout tests and (c) measured values from several full-scale load tests. From these meager field/lab tests and comparisons, we found that: The 'pullout' test offers a less costly than full scale load testing method for assessing skin friction. However, the smaller scale causes the pullout test to be sensitive to hold roughness and construction procedures. Consequently, pullout f_su values can unconservatively over predict full-scale f_su values.

Subject Headings: Load tests | Full-scale tests | Pullout behavior | Skin friction | Load factors | Field tests | Drilled shafts

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