Abstract: To improve the fineness, accuracy, and stability of tunnel lining internal defect detection, and reduce the risk of leakage and misdetection, an elaborate tunnel lining quality inspection method based on ultrasonic phased array is developed. Comprehensively considering the defects distribution within lining arch space and the equipment capacity, a full-coverage continuous elaborate inspection approach is proposed based on regulate inspection grid and scanning mode, therefore balancing detection efficiency and fineness. Benefiting from the multiple coverage acquisition and synthetic aperture focusing imaging properties of the ultrasonic phased array technology, the signal-to-noise ratio and resolution of the detection data can be effectively improved, compared to conventional point-by-point tapping and limited-lines radar detection. As a result, the fineness and imaging effectiveness of the lining internal defects detection can be enhanced. This method is applied to a practical tunnel to perform elaborate lining inspection within the scope of longitudinally 14 m × circumferentially 4 m at the tunnel crown, the inspection ability of the method proposed is verified from detecting 14 mm-diameter rebar and central-embedded water-stop belt. The internal structure of the tunnel lining is demonstrated in three-dimensional image, contributing to accurate identification of the lining internal defects.

Key words: tunnel lining, elaborate inspection, ultrasonic phased array, internal defects, three-dimensional imaging