Resumen
A mathematical model for an outer soil, multi-defects pipe pile, and inner soil dynamic interaction system is established to research the influences of multi-defects on the vibration of a pipe pile. The dynamic impedance of the pipe pile is deduced by applying a Laplace transformation method and an impedance recursive technique. Then, the velocity response at the pile head is further obtained using the inverse Fourier transform method. Moreover, parametric analyses are conducted to research the influences of the type, degree, distribution, length, and depth of multi-defects on the vibration of the pipe pile. The results indicate that the characteristics of multi-defects appear different, with amplitude differences and reflected signal features on the velocity admittance and velocity response curve, respectively. This means that the obtained analytical solutions and relevant results can be used to detect multi-defects of pipe piles using the different appearances of the velocity admittance and velocity response curve, as measured in engineering practice.