ABSTRACT
The axial load-carrying capacity of an open-ended pipe pile is developed through friction along the internal and external walls of the pile combined with end-bearing resistance directly beneath the pile annulus. Due to the constrained nature of the internal soil core, or soil plug, the majority of the internal friction develops within 2-3 diameters of the pile toe. The base resistance of an open-ended pile is defined as the combination of the end-bearing stress beneath the pile plug, qplug, and the pile annulus, qann. During installation, an open-ended pile can be fully coring or it can experience various degrees of plugging, preventing the full intrusion of soil into the pile. A plugged pile will cause more displacement and densification to the soil as it penetrates than a fully coring pile, thus generating a higher resistance. The degree of plugging which occurs during installation can be quantified by the Incremental Filling Ratio (IFR) which is defined as the rate of change of height of the soil plug with respect to pile penetration (IFR = 1 when pile is fully coring and IFR = 0 when pile is fully plugged). Laboratory and field studies (Gavin & Lehane 2003; Xu 2007; Paik & Lee 1993, and others) have demonstrated that plugging during installation strongly influences both the base and external shaft capacities.
