Abstract: A quality inspection test on concrete specimens containing construction joint defects and a sealing test of a scaled utility tunnel are conducted to investigate the application effect of ultrasonic computed tomography (UCT) technology for the defects detection in utility tunnel construction joints. The results show the following. (1) The uniplanar UCT inspection technique exhibits a high accuracy in construction joint defect detection and compactness evaluation. (2) It is assumed that there is a hole defect area within the joint surface when the mutation value of the ultrasonic pulse velocity (UPV) within the length of construction joints exceeds 1 000 m/s. (3) The quality evaluation criterion of bonding based on UPV color is proposed. Further, construction joints are considered to have poor bonding quality when the UPV standard deviation is >250 m/s and the intermittent areas of color banding are obvious. (4) Nonwaterreacting polymer grouting has a good sealing effect on the repairing of construction joints in utility tunnels, and the uniplanar UCT technique can be used to evaluate repairing effect of the polymer grouting in realtime.

Key words: utility tunnel, concrete construction joints; ultrasonic computed tomography, defect detection, polymer grouting