Numerical evaluation of drained and undrained load carrying capacity of soil plug in open-ended pipe piles

Open-ended pipe piles are widely used in marine construction, coastal engineering projects, ports, and offshore structures. When an open-ended pile is driven in the soil, a soil column (or soil plug) is formed within the pile. This soil plug contributes to the ultimate plug capacity of pipe pile by offering end-bearing resistance. In this study, the undrained plug capacity factor (Ncu) and drained plug capacity factor (Nc) is evaluated for axially loaded open-ended pipe piles by using finite element limit analysis. The plug capacity factor is evaluated by considering different L/D ratio, h/D ratio, αi, and ϕ, where L = length of open-ended pipe pile, h = height of soil plug, D = diameter of open-ended pipe pile, αi = coefficient of friction between soil and pipe pile, ϕ = friction angle of soil. The undrained soil plug capacity of open-ended pipe pile is evaluated considering the Tresca model and the drained capacity is evaluated considering the Mohr-Coulomb model for soil; and corresponding failure planes are also evaluated. Present study results on the plug capacity of the open-ended pipe pile are presented as design charts for its application in offshore engineering projects.