Tunnel contour detection during construction based on digital image correlation

Abstract During the tunnel construction process, contours of primary supports and secondary linings of the tunnel need to be tested to ensure that their quality meets the designed requirements. Traditionally, one total station is used to measure the three-dimensional (3D) coordinates of the measuring points of a cross section of the tunnel to check whether there are any intrusions. This traditional method has some disadvantages, such as few measuring points, low precision, heavy workload and long working time. In order to avoid these shortcomings, a method combining three-dimensional digital image correlation (3D-DIC) and angle feedback scanning mechanism that measures the 3D topography of tunnels during construction is proposed in this paper. In order to reduce the systematic deviation caused by the nonstandard positional relationship between the camera and the rotational axis, a calibration method is proposed and implemented to calibrate the positional relationship between the camera and the rotational axis. The proposed device is fabricated, and a tunnel is measured at the construction stage. The scanner only takes about 30 s to operate. When measuring the tunnel with an inner diameter of about 14 m, the overall 3D reconstruction accuracy of the device is better than 10 mm.