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Numerical modeling of centrifuge cyclic lateral pile load experiments

Nikos Gerolymos¹ , Sandra Escoffier² , George Gazetas¹ and Jacques Garnier ²

1. Civil Engineering, National Technical University, Athens, Greece

2. Laboratoire Central des Ponts et Chauss¨¦es, Nantes, France

Abstract: To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand
and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chauss¨¦es. Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately square-root variation of soil stiffness with depth was obtained from indirect in-flight density measurements, laboratory tests on reconstituted samples, and well-established empirical correlations. The tests were simulated using a cyclic nonlinear Winkler spring model, which describes the full range of inelastic phenomena, including separation and re-attachment of the pile from and to the soil. The model consists of three mathematical expressions capable of reproducing a wide variety of monotonic and cyclic experimental p -y curves. The physical meaning of key model parameters is graphically explained and related to soil behavior. Comparisons with the centrifuge test results demonstrate the general validity of the model and its ability to capture several features of pile-soil interaction, including: soil plastification at an early stage of loading, ¡°pinching¡± behavior due to the formation of a relaxation zone around the upper part of the pile, and stiffness
and strength changes due to cyclic loading. A comparison of the p¨Cy curves derived from the test results and the proposed model, as well as those from the classical curves of Reese et al. (1974) for sand, is also presented.

Keywords: centrifuge test; Winkler model; p-y curves; cyclic loading; pile-soil separation/gapping; nonlinear response; experimental validation
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