Analytical Solution of Wave Propagation in Large-Diameter Piles for Low Strain Integrity Testing

This paper presents an analytical solution on wave propagation in a large-diameter pile for low strain integrity testing. Based on three-dimensional (3D) wave equation that considered the vertical displacement and combined the initial and boundary conditions, the frequency-domain analytical solution on the transient dynamic response of large-diameter pile in low strain integrity testing is deduced by Laplace transformation and separation of variables method. The time-domain dynamic response is obtained by numerical inverse Fourier transformation. A case history is studied to analyze the 3D effects on pile head. The results indicate that the velocity waveforms are different among the measure points with various distances apart from pile center. The peak values and arrival times of incident waves have a greater difference, but the reflected waves from pile bottom have little difference. The phases and peak values of high-frequency interference waves have some differences but the interference frequencies are almost the same. The time-delay is conspicuous when r<2/3R, but it is no longer enhanced when r≥2/3R. The peak value rapidly decreases as the increase of r from 0 to 0.2R. However, the peak values from 0.2R to R have little difference. The measured waveform can be well simulated by the analytical solution.