Mechanisms and prediction of entire soil plug evolution during open-ended pile installation in clay soils

The development of a soil plug is significant during the installation of open-ended piles, particularly those with high aspect ratios. Predicting the soil plug length, plug stress and penetration resistance presents challenges in practical applications. This paper investigates the entire evolution of the soil plug and its effects on the plug resistance of jacked open-ended piles in clay both numerically and analytically. Numerical analyses are undertaken with a large-deformation finite-element method to reveal the mechanisms behind the soil plug evolution. The degree of soil plugging is quantified by a mechanism-based approach with force equilibrium and adjusted bearing capacity theory, through which the incremental filling ratio and penetration resistance against installation depth can be estimated. The effectiveness of this framework has been confirmed through comparisons with field testing and numerical simulation. The method is straightforward to implement in practical applications.