Pile group foundations are used in most foundation solutions for transportation structures. Rigorous and reliable pile design methods are required to produce designs whose level of safety (probability of failure) is known. By utilizing recently developed, advanced, two-surface plasticity constitutive models, rigorous finite element analyses are conducted. These analyses are for axially loaded single piles and pile groups with several pile-to-pile distances in various group configurations installed in sandy and clayey soil profiles. The analyses shed light on the relationships between the global response of the pile-soil system (development of shaft and base resistances) and the behavior of local soil elements (e.g., shear band formation). The influence of the group configuration, pile-topile spacing, soil profile, and pile head settlement on the group effects are studied. Mechanisms of pile-soil-pile interactions in pile groups are revealed. Pile efficiencies for individual piles and the overall pile group are reported for use in pile group design. The instrumentation, installation, and static and dynamic testing of a closed-ended, driven pipe pile in Marshall County, Indiana is documented. The test results along with two other case histories are used to verify the new Purdue pile design method. Probabilistic analyses are performed to develop resistance factors for the load and resistance factor design, LRFD, of pile groups considering both displacement and non-displacement piles, various soil profiles, and two target probabilities of failure. The pile design equations, pile group efficiencies and resistance factors together form the LRFD pile design framework. Two step-by-step design examples are provided to demonstrate the LRFD pile design procedures for single piles and pile groups.

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pile groups, pile group-soil interaction, group efficiencies, group effect, piling, pile resistance, pile group design, load and resistance factor design, LRFD

SPR Number


Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, Indiana

Date of this Version