Group Efficiency of Piles Driven Into Sands: A Simple Approach

by José L. M. Clemente, Geotech Engr, Columbia, United States,
Sayed M. Sayed, Geotech Engr, Columbia, United States,



Document Type: Proceeding Paper

Part of: Geotechnical Engineering Congress—1991

Abstract: A simplified analysis for computing group efficiency of circular displacement piles in sands is presented. Pile installation is assumed to cause soil displacements in the horizontal direction only, thus yielding an axisymmetric problem. The soil surrounding the pile is modeled as a weightless nonlinear elastic material. Material nonlinearity is handled in a simplified manner by adopting secant shear moduli defined in terms of a proportionality coefficient and a softening factor. The resulting equilibrium equation is solved analytically and an expression is obtained which is also conveniently presented in graphical form. The derived expression can be used to estimate horizontal stress changes and is incorporated into a simple procedure to estimate the ultimate load or efficiency of driven pile groups. An illustrative example is provided and comparisons are made between calculated and measured efficiencies of full-scale group load tests in sand.

Subject Headings: Load tests | Displacement (mechanics) | Pile groups | Sandy soils | Ultimate loads | Load factors | Driven piles

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