A study on the application of the parallel seismic method in pile testing

• Adopt the elastodynamic integration technique for parallel seismic testing of pile.
• Present a more accurate method for determining the pile-length based on the ray path theory.
• Effectively evaluate the longitudinal wave velocities in pile and soil mass according to the time–depth curves.
• Compare parallel seismic testing with the low-strain pile integrity testing for the pile with a cap.
• Accurately identify and locate the defects in certain piles by using parallel seismic testing.

Parallel seismic testing of pile is theoretically studied using the ray path theory and the elastodynamic finite integration technique (EFIT). According to the basic principles and the testing process, the practical pile model is simplified as a space axisymmetric problem, and the definite solution can be obtained with given boundary and initial conditions. The EFIT is a simple numerical tool and employed in this study. A more accurate method for determining the pile length is presented based on ray path theory, the effects of pile-to-borehole distance and other parameters on the testing results are numerically analyzed in detail. In addition, parallel seismic testing is compared with the low-strain pile integrity testing with respect to the pile with a cap. The former has good performance in determining the pile length. Also, neck or expansion part in the pile body is well able to be identified.