Impulse response evaluation of drilled shafts with pile caps: modeling and experiment

Impulse response, a nondestructive surface reflection technique, offers a way to assess the quality and integrity of deep foundations. While the impulse response test is a straightforward method to implement, interpretation of the data is often difficult. The response of a shaft will be affected by construction conditions, accessibility and quality of the concrete, as well as by gross defects in geometry. As a result, test responses seldom resemble the ideal theoretical response. The difficulty is increased when the accessibility of the shaft is limited by the presence of a pile cap or other structures. This study progressively develops and builds two-dimensional (2-D) and three-dimensional (3-D) finite element models of experimentally tested shafts to identify key structural features that can be modeled and captured experimentally. For shafts with pile caps, the model helped confirm previous interpretations of the experimental data presented in this paper, identifying the shaft base, a defect, and the base of the pile cap.Key words: nondestructive testing, quality assessment, quality assurance, impulse response.