Large-scale evaluation of concrete repair by three-dimensional elastic-wave-based visualization technique

摘要

The development of elastic wave tomography technique using three-dimensional ray tracing and identification algorithm is discussed. The technique introduces hexahedral elements for isoparametric mapping of irregular structural shapes, for which the distribution of slowness of ray path is computed using simultaneous iterative reconstruction technique. In addition, the three-dimensional computation capability of the technique facilitates detailed assessment of any cross section within the measured perimeter, which is a main advantage compared to the more conventional two-dimensional elastic wave tomography. The newly developed technique was applied for evaluating the repair of concrete piers of a water intake facility by taking the transit time of primary waves (P-waves) as data for reconstruction of velocity distribution of the measured region. In this particular field implementation, multichannel elastic wave tomography measurements were carried out at selected areas on the piers before and after the repair to study the change of velocity distribution. Simple quantitative analysis for improvement of concrete Young's modulus due to the repair was also examined. Findings obtained from field measurement and analysis confirmed the usefulness of the technique for large-scale in situ implementations.