Effect of Source Application on Sonic Echo/Impulse Response Tests Applied to Steel H-Piles

The sonic echo/impulse response (SE/IR) method is a versatile nondestructive method for evaluating the conditions of unknown bridge foundations. Previous studies have shown that the method has satisfactory performance in determining the length of concrete drilled shafts and wood piles. However, no significant success with steel H-piles has been reported due to the specific cross-section shape of such piles. Although previous studies have reported unsuccessful SE/IR tests, they have not discussed the effect of factors that can improve the methodology. In this study, the effect of hammer-tip type on obtained signals was investigated. SE/IR tests were conducted on two steel H-piles of a highway bridge with different striking hammer tips to examine if interpretable signals could be achieved. The results show that the hard tip with a contact time equal to $\mathrm{1,420}–\mathrm{1,880}\mathrm{\mu s}$ did not produce interpretable results. However, when a softer hammer tip with a longer contact time equal to $\mathrm{5,520}–\mathrm{6,840}\mathrm{\mu s}$ was utilized, the echoes from the pile toe were identifiable and consequently the length of the steel H-piles could be determined. These results show that SE/IR can be used to determine the depth of H-piles if a proper hammer tip is selected.