Determining Length of Pile Foundations by Analyzing Response to Lateral Hammer Impact-PPT Presentation

PPT Presentation

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The presentation introduces Effective Dispersion Analysis of Reflections (EDAR), a nondestructive method for estimating pile length from the response to a hammer impact. The method addresses the need to assess bridge foundations where scour may reduce embedment or construction records are missing.<br /><br />A lateral impact generates flexural waves, whose velocity varies with frequency, as well as longitudinal waves. EDAR analyzes wave dispersion and reflections using measurements from accelerometers. Laboratory tests on a 19.4-foot reinforced-concrete-filled steel tube pile, embedded 13.67 feet in relatively loose soil, produced length estimates with an average error below 5%.<br /><br />Initial field testing of a 9.1-meter pile underestimated its length because soil caused different attenuation of longitudinal and transverse waves. The researchers modified the analysis to treat the waves separately: the initial arrival, dominated by transverse waves, is used to estimate material properties and wave velocity; the reflected signal, dominated by longitudinal waves, is then used to estimate pile length. The revised method brought field estimates within 10% of the actual length.<br /><br />The findings suggest that EDAR can account for dispersive waves and, with correction for soil-related attenuation, provide reliable pile-length estimates. Further research is needed to examine other boundary conditions and discontinuities, and to extend the approach to timber, steel, and other foundation types.

Keywords

Effective Dispersion Analysis of Reflections

EDAR

pile length estimation

nondestructive testing

bridge foundations

hammer impact

wave dispersion

accelerometers

flexural waves

longitudinal waves