The dynamic lateral response of pile groups

by Burr, J P

Abstract (Summary)
This study involves an investigation into the effects of pile spacing on the lateral dynamic response of pile groups. The first part of the study consists of experiments on thirteen 2 by 2 pile groups with three different pile diameters and pile spacing to diameter ratios of 2.25 to 15.0. Static, plucking and dynamic tests were performed on these groups and six single piles at two separate sites, one with stiff soil and one with soft soil. - The results from these experiments showed that pile-soil-pile interaction effects are significant up to spacing to diameter ratios of between 12, for the stiff site and 16, for the soft site. Beyond these values the interaction effects were negligible and the pile groups behaved as four isolated piles connected by a pile cap. These experiments are the first to prove that the spacing to diameter ratio is the important parameter in this relationship as previous experiments into interaction effects were performed using the same diameter piles for all groups. Other results from these experiments show that dynamic lateral loading of piles and pile groups causes a significant reduction in the soil resistance due to nonlinear effects and gapping at the pile-soil interface. These effects stabilised if the load was not increased. The second part of this study involves the development of a simple theoretical analysis to model the response of the pile foundations tested in the first part. The theory assumes linear elastic behaviour from all materials and models the pile foundations as equivalent single degree of freedom oscillators. The analysis produced good predictions of the static and dynamic responses of both the single piles and the pile groups. The results indicated that the static group response could be predicted from the single pile tests but this relationship was not available for the dynamic response. It was felt that the pile-soil gapping from the dynamic tests had a greater effect on the free headed single piles than the fixed headed pile groups. A constant value of Young's modulus (the main soil resistance parameter) for each site produced accurate predictions of the dynamic response of the pile foundations. The values of Young's modulus that were required to produce accurate results were found to be typical for laterally loaded pile problems. Finally this simple theory was tested against a more complicated commercially available dynamic analysis program and found to produce comparable results
Bibliographical Information:


School:The University of Auckland / Te Whare Wananga o Tamaki Makaurau

School Location:New Zealand

Source Type:Master's Thesis



Date of Publication:01/01/1994

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