| Based on the Timoshenko beam model, a dynamic model of a defective pile in non-uniform soil subjected to transient lateral loads was developed. The frequency response function of the pile-soil system velocity was analytically obtained in the frequency domain, and the expression for the pile top velocity in the time domain was derived using Fourier transform. Then, parameters for four types of defective piles—reduced diameter, expanded diameter, segregated, and broken piles—were set, and frequency domain velocity admittance curves and time domain pile top velocity curves were plotted for comparison and analysis. The lateral vibration characteristics of the four types of defective piles and the influence of various factors on the defective piles were elucidated. The typical waveform characteristics and applicable range of the time-domain velocity curve for identifying shallow defects in the pile under transient lateral excitation were clarified. The results show that the velocity admittance can effectively represent the dynamic characteristics of the lateral vibration of each defective pile in the pile-soil system. The numerical increase or decrease in the fundamental frequency and peak amplitude of reduced diameter, expanded diameter, segregated, and broken piles, as well as the distortion of the waveform in the difference between adjacent peak frequencies and peak-valley differences, can all be used as criteria for identifying defective piles. When identifying shallow defects, the shear wave excited by transverse vibration has a shorter wavelength and is more sensitive to shallow defects. Especially under high-frequency excitation, the blind zone of the reduced diameter pile can be reduced to within 0.5m, the expanded diameter pile to within 0.3m, the segregated pile to within 0.5m, and the broken pile to within 0.5m. This significantly reduces the blind zone range of shallow defects when testing piles with low strain. |
