Аннотация:Non-destructive testing by cross-hole sonic logging is used worldwide to assess the structural integrity of cast-in-situ deep foundation elements. However, there is still a lack of consistency in the interpretation of test results. The cross-hole sonic logging rating criteria are conjectured based on experience, without rigorous studies or solid evidence to justify the current first arrival time and energy thresholds. Among industry professionals, there is no consensus on the importance of the energy criterion, nor is there clarity on how the location and shape of defects affect the first arrival time and energy. This study aims to reduce this uncertainty by providing documented evidence regarding industry speculations and establishing a scientific basis for decisions resulting from the tests. In this study, two-dimensional numerical modeling was applied using the finite element method to investigate how the size, location, and shape of the defect affects its detectability by cross-hole sonic logging, as well as the ability of the method to detect defects outside the reinforcing cage and debonding issues. The modeling results indicate that the first arrival time depends significantly not only on the size of the inclusion but also on its shape and position within the cross section, providing some quantification of this influence. To avoid missing defects, this study clearly demonstrates the need to consider relative energy as an evaluation criterion in conjunction with the first arrival time. Furthermore, the study reveals that energy calculations, utilizing ASTM’s recommended time interval, offer a more effective method for evaluating potential defects compared to using the entire signal.
