Drilled-Shaft Integrity by Wave Propagation Method

Compression wave propagation methods provide an economical and rapid nondestructive means of assessing the structural integrity of drilled shafts shortly after construction. Several source-receiver configurations can be employed. The most successful configuration used involved a mechanical hammer with which a vertical impulse was applied at the top of the shaft and vertical velocity transducers which were cast in place in the shaft at preselected depths. Successful application of this configuration required identification of reflected compression wave arrivals with transducers allowing travel times of reflected waves to be used with propagation velocity to determine elevations of reflection points. Examples of the results for tests with sound shafts and for shafts with known defects of different sizes are presented.