The settlement and deformation monitoring for existing tunnels would encounter the difficulties in sensor installation and health evaluation in real time. Thus, it is necessary to develop effective methods for settlement and deformation measurements in the existing tunnels. This study proposed a more practical tunnel deformation monitoring theory and developed remote wireless tunnel deformation real-time monitoring and early warning system based on infrared laser ranging technology and cable sensing technology. The system could monitor the settlement and deformation of the tunnel in real time from a long distance and transmit the deformation data wirelessly in real time; then, three-dimensional space model of tunnel deformation was established, which intuitively and comprehensively reflected the actual deformation of the tunnel and intelligently identified the deformation. Finally, based on the practice of deformation control during tunnel excavation at Xiaohongshu Station of Wuhan Metro Line 8 of China, the measurement results of this new method were compared with the measurement results of particle image velocimetry technology (PIV), the reliability of the new tunnel deformation monitoring method was proved, the settlement error of each monitoring point was found to be less than 1 mm, and the deformation trend was consistent with the actual deformation. The results of this research could provide useful guidance for tunnel deformation monitoring.
The settlement and deformation monitoring of subway tunnels had difficult in long-distance and real time measurement. This study proposed an optic-electric hybrid sensor based on infrared laser ranging technology and cable-sensing technology. The working principle, hardware layer, design details, laboratory calibration and field validation were presented and discussed. The optic-electric hybrid sensor implemented the real-time intelligent analysis modulus for the whole system which could analysis the measurement errors and improve the accuracy. The laboratory calibration tests were carried out and the results shown that the hybrid sensors had measurement resolution of 1 mm with the maximum measurement range of 100 m. A remote real-time intelligent monitoring system is established based on the hybrid sensors. The system contains an edge computing module, real-time communication module and warning light signal with three colors. The stability of data acquisition and transmission of the intelligent control monitoring system under long-term conditions was examined. Test results shown that the system was quite stable for the long-term measurement. The whole system was verified in a constructing subway tunnel of Wuhan Metro Line 8, China. According to the field monitoring results, the deformations and the state of health safety of the tunnel was evaluated. The results of this study could provide useful guidance for tunnel deformation monitoring and has great practical value in civil engineering.
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