Experimental study on detecting pile defects by parallel seismic method

The parallel seismic method has been successfully used to detect the depth of the existing pile, but the effect of this method on detecting the pile defects is not clear. In this paper, a large-scale model pile experiment was designed and carried out to analyze the stress wave transmission corresponding to various defects, and the influence of test distance and excitation position on the stress wave transmission was further discussed. The results show that the parallel seismic method can effectively identify the serious defects when the test borehole is close to the test pile, and the increase of test distance will greatly increase the difficulty of detecting pile length and defect identification. The broken pile and the necking can cause the decrease of wave velocity and the prolongation of the first arrival time, and the abnormal characteristics of stress wave group corresponding to the slight defects are not significant. When the bearing stratum of the pile is hard bedrock, the sediment at the pile tip may lead to the second mutation of the slope for the fitting line of the first break wave. When the defect is close to the shortest transfer path of stress wave, the abnormal characteristics of first break wave are more obvious.