The installation resistance of open-ended piles

This paper presents the measurements made during the installation of an instrumented open ended model pile jacked into soft clay at a site in Belfast, Ireland. The importance of appropriate instrumentation is emphasized by comparing the measured resistance with those predicted using traditional bearing capacity calculations. The base and shaft resistance were accurately measured using a strain gauged twin walled pile that incorporated an annular stress sensor. The degree of plugging, quantified through the Incremental Filling Ratio (IFR), was shown to influence the mobilized plug capacity, whereas the annular stress and external shaft capacity were independent of plug development. The shaft stress is comparable to that mobilized by a closed ended pile at the same site. These field results suggest no influence of end condition on the installation shaft resistance of a closed and open ended pile installed in Belfast soft clay.