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Measurement and analysis of long-tunnel cross-sectional deformation using multi-sensor integration

A long tunnel is a typical linear man-made infrastructure. The shape, especially the cross-sectional shape, and geometric parameters of the tunnel are very important for the safety of transportation. A multi-sensor integration approach is presented to survey the shape of the tunnel dynamically. With efficient collection of high-precision spatial points of structure surface, a laser scanner is widely used for measuring the structure's three-dimensional geometric and deformation. In this article, two laser scanners and other position and orientation sensors, such as DGPS, IMU, and DMI, are integrated to form a MSI measuring system. With position and orientation sensors, the position and orientation of the laser scanners could be acquired dynamically, even in the tunnel where a GPS signal is out of reach. For fusing data collected from different sensors, data are generalized into a unified coordinate system. In our study, data from the laser scanner are first converted from the laser scanner coordinate system to the vehicle coordinate system. Then, vehicle coordinates are converted into geodetic coordinates by referencing the IMU coordinate. Calibrations are carried out in advance to obtain the parameters of conversion between coordinate systems. A time-domain tunnel deformation evaluation model is created on the basis of cross-sectional area change detection, where matching-based deformation detection (MDD) algorithm has been proposed for calculating the deformation area of two cross-sectional polygons. This article also reports a test to use MSI measuring system for Wuhan Yangtze River highway tunnel measurement. Results of the precision analysis verify the reliability of the proposed tunnel deformation evaluation model and the validity of the MDD algorithm.