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

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The paper examines how pile installation practices affect the side resistance of driven pipe piles in plastic soils. Using case histories from pile load tests, the authors compare measured resistance with a SHANSEP-based method, which relates normalized side resistance to soil overconsolidation ratio. They propose a construction influence factor (CI) to estimate installation-related reductions in resistance.<br /><br />The case histories indicate that side resistance can be reduced by re-driving piles after setup, prolonged or interrupted installation, slow jacking, vibratory hammer use, and driving through long surface casings in soft soils. These practices can disturb or weaken the soil–pile interface; casing-related pile movement may also reduce contact with the surrounding soil. Open-ended piles that core through the soil, particularly large-diameter piles requiring multiple splices, may be especially vulnerable. The observed reductions are associated with installation procedures, rather than necessarily with pile length itself.<br /><br />For preliminary design, the authors suggest a CI of 1.0 for piles driven nearly continuously with an impact hammer, and indicative values around 0.5–0.7 for damaging practices such as vibratory installation, slow jacking, or re-driving. These factors are approximate: the available case histories are too limited to establish their statistical reliability, and actual effects vary with site and installation conditions.<br /><br />The authors recommend minimizing pauses, splices, re-driving, and vibratory driving in plastic soils where practicable. Where such methods are required, designers should account for possible capacity loss and use pile load tests to verify performance. Load-test records affected by damaging installation practices should also be distinguished from data used to predict capacity for continuously impact-driven piles.

Keywords

pile installation

side resistance

driven pipe piles

plastic soils

pile load tests

SHANSEP

construction influence factor

vibratory driving

re-driving

soil-pile interface