Numerical Simulation of Ultrasonic Pile Integrity Testing

Abstract

Noncompliance of the form or material of piles with the requirements of project documentation may lead to an unacceptable decrease in the bearing capacity of the foundations of buildings and structures being constructed. Field tests are carried out using nondestructive geophysical methods in order to control the quality of cast in-situ reinforced concrete piles. Ultrasonic monitoring of concrete integrity is based on the analysis of the parameters of elastic waves excited and recorded in the pile body using sensors immersed in the access tubes installed in the reinforcement cage. Numerical simulation of the propagation of elastic waves has been performed to clarify approaches to the interpretation of ultrasonic data in the COMSOL Multiphysics software. The studies were conducted for a series of two-dimensional models of bored piles without defects, with soil inclusions, or with a debonding of the access tubes from the concrete. Conclusions are drawn about the possibilities and limitations of the method. The influence of the location and geometrical dimensions of defects and of the violation of adhesion of access tubes to concrete on the results of measurements is demonstrated. The need for additional research of anomalies by crosshole tomography prior to drawing conclusions about the possibility of further use of the piles as part of a foundation is indicated. General recommendations are given regarding the number of access tubes to be arranged in a pile and the choice of time interval for calculating the attenuation. It is shown that it is incorrect to calculate the strength of the pile material from the values of wave propagation velocity.