Experimental study for the evaluation of stress wave approaches on a group pile foundation

This paper investigates the relative performance of the sonic echo (SE), impulse response (IR), and parallel seismic (PS) tests using a field constructed pile foundation incorporating simulated defects. Tests were performed before and after the construction of a pile cap. According to the experimental results, the SE method has the best performance with regard to defect detection in an isolated pile. The results of the PS test were more consistent with regard to the length determination of the piles with a cap than those obtained using the SE and IR methods. The pile length estimated from the PS method increases with increasing borehole-to-pile distance, but this over-estimation can be reduced by applying length correction factors, thus providing more conservative estimations of the pile length. The two length correction approaches for the PS test produced similar results.