The Behavior of Long Piles Under Compressive Loads in Sand

Abstract

Laboratory load tests were conducted on piles 15.9–38.1 mm in diameter and up to 1.8 m long in a compact dry sand. The piles were buried in the sand stratum during sand placement. Two conditions of test were imposed—in one the pile was free to settle as the sand was placed around it and in the other the top end of the pile was rigidly clamped thus preventing any movement of the pile during sand placement. The piles were provided with sensitive axial load transducers at their base and at seven positions along their length.During test preparation a residual force system was locked in the pile and it was found that this initial residual state controlled the subsequent load and movement behavior of the pile. Data are given which show the mechanics of load mobilization and sharing for piles of different length–diameter ratios between 10 and 112, different axial flexibilities, and different diameters. In addition one series of tests examined the significance of footings located at regular intervals along the pile shaft. It is shown very clearly that extensive arching occurs along the lower lengths of the piles thus confirming earlier work of Vesić. The multiunderreamed pile is much more efficient than a straight sided pile of equal diameter. The mechanism of load development in a pile is not in agreement with any of the standard pile bearing capacity theories but agrees with concepts presented earlier by the authors. The significance of the experimental findings is discussed.