NONDESTRUCTIVE EVALUATION BY ANALYSIS FOR DENSITY OF CRACK IN TUNNEL UNDERGROUND STRUCTURES WITH TUNNEL SCANNER

摘要

This study has focused on the method of stateestimation in tunnel and underground structures by analyzing density of cracks. Reliability on this technique is decided by exact measurement and analysis of cracks. The tunnel scanner, one of the nondestructive technologies, is used by high resolution CCD (charge-coupled device) camera because accurate data could not be acquired by the conventional visual inspection method. This method can get reliable image data through detailed shooting on the surface of the target structures and analyze accurate information (width, length, location etc.) of cracks by image processing. The crack density was analyzed by considering section type of structures, length of span and expansion-joint and by using numerical location and distance of cracks like width and length. Cracked area, which is a basis of crack density analysis, was calculated 0.25 m width per crack length. We can specially manage a zone to be concentrically generated through a distribution chart of crack density to be analyzed over all structures. The analyzed data, which were detected by nondestructive tunnel scanner, proffered information for reasonable judgment in evaluating conditions of tunnel and underground structures, and further, they are used as reliable information to determine safety diagnosis, precise safety diagnosis or priority of repair and reinforcement works.