Use of Case Histories to Illustrate the Effect of Installation Activities on the Side Resistance of Pipe Piles in Plastic Soils

Abstract

This paper presents observations of the influence of pile installation methods on the measured side resistance of driven pipe piles bearing in plastic soils. Pile installation practices that can reduce the capacity of completed piles in plastic soils from that calculated include re-driving of piles after partial or full dissipation of excess pore water pressure, long installation times, slow jacking, the influence of surface casing in soft soils, and the use of vibratory hammers. Selected case histories are used to illustrate how deviations from rapid and nearly continuous pile installation can result in poor performance. Designers and Contractors need to be more aware of the damaging effects of these practices and that the selected design approach may not effectively consider the selected installation procedures. Where project requirements dictate use of these installation approaches that damage pile side resistance, the proposed construction influence factors may be used to modify a SHANSEP-based side resistance method to estimate the potential reductions in side resistance associated with the selected approach. Although the number of case histories available are too few to characterize the reliability of the construction influence factor approach, the cases sufficiently demonstrate the damage that can occur when these practices are used and the importance of construction procedures for driven pipe pile foundations that minimize or avoid damage to side resistance and to highlight where special design and testing are merited.