Theoretical and Experimental Study on Multiparameter Criteria of Ultrasonic Method for Foundation Piles

Abstract

As one of the important methods to survey the foundation pile integrity in most engineering industries in China, ultrasonic testing (UT) has such advantages as determining the position and scope of defects accurately and good operability. In this paper, on the basis of the in-depth study of China’s industrial standards, main parameters for evaluating pile integrity in each standard were extracted, features and deficiencies of each parameter were analyzed in detail, and a multiparameter identification method of ultrasonically testing foundation pile integrity, which takes wave velocity, amplitude and basic frequency as the analytical parameters and outputs quantitative results, was proposed as an effective supplement to the ultrasonic testing of foundation pile integrity. This method has been applied to the result analysis of more than 800 engineering piles, and has obtained high consistency by comparing those results with core drilling results. Among them, $$K_{(i)}$$, the evaluation index of pile integrity with the pile complete and the buried acoustic pipe flat, is basically closed to the range $$1 \le K_{(i)} \le 1.35$$; when $$K_{(i)} > 1.35$$, all others, except for several points, are $$K_{(i)}$$ dispersion caused by head wave interpretation errors; when $$0.85 \le K_{(i)} < 1$$, all acoustic lines within this range reflect slight or obvious abnormalities of sound velocity and amplitude and obvious distortion of waveforms, that is, this acoustic line has slight or obvious defects; when $$K_{(i)} < 0.85$$, all acoustic lines within this range reflect serious abnormalities of sound velocity and amplitude and obvious distortion of waveforms, that is, this acoustic line has serious defects. Conclusion: This method can effectively reduce the impact of changes in critical values of wave velocity and amplitude caused by the misinterpretation of the head wave position, thus providing a rapid and accurate evaluation for the ultrasonic testing of foundation pile integrity for later engineering practice reference.