Abstract
Pile foundations are frequently used in very loose and weak deposits, in particular soft marine clays deposits to support various industrial structures, power plants, petrochemical complexes, compressor stations and residential multi-storeyed buildings. Under these circumstances, piles are predominantly subjected to horizontal dynamic loads and the pile response to horizontal vibration is very critical due to its low stiffness. Though many analytical methods have been developed to estimate the horizontal vibration response, but they are not well validated with the experimental studies. This paper presents the results of horizontal vibration tests carried out on model aluminium single piles embedded in a simulated Elastic Half Space filled with clay. The influence of various soil and pile parameters such as pile length, modulus of clay, magnitude of dynamic load and frequency of excitation on the horizontal vibration response of single piles was examined. Measurement of various response quantities, such as the load transferred to the pile, pile head displacement and the strain variation along the pile length were done using a Data Acquisition System. It is found that the pile length, modulus of clay and dynamic load, significantly influences the natural frequency and peak amplitude of the soil-pile system. The maximum bending moment occurs at the fundamental frequency of the soil-pile system. The maximum bending moment of long piles is about 2 to 4 times higher than that of short piles and it increases drastically with the increase in the shear modulus of clay for both short and long piles. The active or effective pile length is found to be increasing under dynamic load and empirical equations are proposed to estimate the active pile length under dynamic loads.
Highlights
The increasing use of pile foundations in power plants, petrochemical complexes and earthquake prone areas, offshore platforms and our limited knowledge and understanding of nonlinear soil-pile-structure interaction under dynamic loads, have contributed to the recent interest and activity in the dynamic analysis of soil-pile-structure systems
It is found that the pile length, shear modulus of clay and magnitude of the applied force significantly influences the natural frequency of the soil-pile system
Natural frequency substantially increases with the increase in the pile length and shear modulus of clay at low magnitude of the dynamic force due to high stiffness of soil-pile system derived from passive resistance and inertia effect of the soil-pile system
Summary
The increasing use of pile foundations in power plants, petrochemical complexes and earthquake prone areas, offshore platforms and our limited knowledge and understanding of nonlinear soil-pile-structure interaction under dynamic loads, have contributed to the recent interest and activity in the dynamic analysis of soil-pile-structure systems. Few models have been proposed accounting the nonlinear behaviour of soil [4,9,10,18,22,23,25,34,36,37,40] to study the soil-pile interaction under inertial and seismic lateral loads and an overview of various linear and nonlinear methods of dynamic analysis was presented in [3]. These models have been proposed to study the dynamic soil-pile interaction accounting the nonlinear behaviour, a lot need to be still learned through parametric studies and experimental investigations. Analysis and interpretation of experimental data, empirical equations are proposed to determine the depth of maximum dynamic bending moment (z md) and thereby the active pile length under dynamic lateral loads
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