Pile integrity test methods of driven and cast in situ piles have been developed by several researchers using differing equipment and methods. Some methods require expensive special preparations during pile manufacture or installation. Others can be applied to randomly selected piles or to piles selected on the basis of their installation histories. The latter methods are inexpensive, easily applied, and, therefore, routinely applied worldwide. Often, all piles on a site are tested and problem piles are identified for corrective action. These methods, called low-strain tests, use signals from a hand-held hammer striking the pile top, which generates a compressive stress wave in the pile. Stress wave reflections from nonuniformities orthe pile toe are observed at the pile top, processed, and interpreted by the experienced test engineer. The pulse echo method records the pile top velocity as a function of time. The transient response method displays the mobility (i.E., The ratio of frequency spectra ofpile top velocity to force). How both low-strain methods can be combined into one method yielding an optimal amount of information is demonstrated. Recommendations for test preparation and data analysis are given. It is concluded that the new method contains more information than either previous method alone and recommended that analysesbe made in both the frequency and time domains. This paper appears in transportation research record no. 1331, Integrity testing of foundations 1991
Abstract