On the design of instrumented double-wall model piles used to investigate plugging of open-ended pipe piles

Plugging of open-ended pipe piles during installation and loading is an important phenomenon with substantial effects on pile capacity. This paper offers a number of comments related to the design of instrumented double-wall pipe piles that are becoming increasingly popular in research.A double-wall pile consists of two concentric thin-wall cylinders that are rigidly fixed at the top and are free to strain independently of one another elsewhere, with the pile shoe attached to one of the cylinders. Instrumentation that permits defining the state of the stress around the pile is installed between the two cylinders. Pile geometry, location of pile shoe, protection of sensors, radial stress measurements, and pore water pressure measurements are discussed. Measurements indicate that when a pile plugs, load is transferred by arching to the inner pile surface within the first two pile diameters. The data also indicates that a surge in pore water pressure occurs with each hammer blow, which results in a reduction of effective stress and subsequent pile setup.