Evaluation of dynamic behavior of single floating piles embedded in soft clay layer under lateral harmonic and impulse loading

The precise evaluation of dynamic behavior of piles has been pressing issue in geotechnical engineering. Comparison of the various numerical methods with experimental studies shows disagreements in prediction of natural frequencies and pile head displacement responses. Thus, fine-tuning is performed to improve the matching between numerical and experimental responses. This paper gives, a framework to predict dynamic response of single floating piles, under linear elastic conditions, without any adjustment to soil mechanical properties. Harmonic and free vibration tests are performed on single floating piles of different diameters, for obtaining pile head displacement responses and natural frequencies. Numerical simulations are performed using: (1) Reduced Dimension Finite Element Method (RDFEM); (2) 3D closed form solution in frequency domain; and (3) Winkler’s Beam on Spring Foundation (WBSF) model, to verify their ability to simulate dynamic response. Local resonance caused at soil layer natural frequencies are also examined. Effect of soil layer and pile head conditions on dynamic response of piles are also investigated. Seismic cross-hole test is performed to obtain soil dynamic moduli. Good matching of pile head displacement responses and natural frequencies were observed from the experiments, RDFEM and 3D closed form solution. However, predictions by WBSF model showed significant discrepancies. Curvature, bending moment and shear force variation along the pile length, interpreted from experiments and numerical methods, showed bending moment and shear force of long piles are 5 to 7 times higher than those for short piles. Also, bending moment and shear force are maximum at the pile head and at the natural frequency.