DYNAMIC-RESPONSE OF INTACT PILES TO IMPULSE LOADS

The objective of this work was to evaluate the theoretical capabilitie s of the non-destructive impact-response method in estimating the leng th and cross-sectional area of intact piles. Three-dimensional (3-D) a xisymmetric finite element models were developed to simulate the testi ng. The results obtained were compared to one-dimensional solutions to evaluate the importance of 3-D effects. Extensive parametric studies were then performed on piles without defects. In each parametric study , the results from the direct use of time histories of displacements o r velocities, the mobility function and the Fourier transform of the r ecorded displacements (impact-echo method) were compared in order to a ssess their relative advantages and disadvantages. The effects of the relative stiffness of the surrounding soil to that of the pile and of the embedment depth were also investigated for all three methods. In a companion paper the use of these procedures to detect defects such as bulbs (increases in the cross-sectional area of the pile) or necks (d ecreases in area) is studied. (C) 1997 by John Wiley & Sons, Ltd.