Deformation monitoring of noncircular tunnels based on 3D laser scanning

Deformation plays an essential role in the safety control of tunnel construction, especially for tunnels with large deformation disasters. Consequently, tunneling professionals need practical ways to monitor tunnel deformation. However, traditional methods are not yet available for 3D monitoring. This study presents a technology for measuring tunnel deformation on using a 3D laser scanner. This technology includes an automatic noise removal algorithm based on spatial features and a measurement technology of absolute coordinates. For point clouds with different times of section with the same mileage, a point-to-point deformation analysis is performed based on the azimuth. Based on the standard grid of point clouds in the longitudinal and circumferential directions of the tunnel, an overall deformation cloud map of the noncircular tunnel is generated. The use of the proposed method in the construction of the Xinzai tunnel of the express connecting Jianshui and Yuanyang in Yunnan province allows engineers to obtain critical information about deformation. Compared with the traditional monitoring method, the proposed approach can meet engineering requirements well.