Study on real-time sensing and early-warning of construction safety risk for metro crossing passage under Yangtze River

The hydrological conditions are extremely complicated in different cities of China. Especially during the construction of tunnel crossing passage under Yangtze River, the coupled mechanism of the moisture-heat-stress fields is unclear. Due to the high hydrodynamic pressure, the mechanics of the support system and the secondary lining system in crossing passage are dynamic and complex during the process of freezing, excavating, supporting and melting. Once dangerous situations or accidents emerge, it often leads to unpredictable catastrophic consequences. In this paper, a real-time sensing technology for construction safety condition assessment of crossing passage is proposed and applied in the construction of the first metro-tunnel crossing passage under Yangtze River in China. 18 Fiber Bragg Grating (FBG) sensors are installed in the frozen soil, the of tunnel segment structure and the crossing passage. A real-time early-warning system is developed based on the online collection and analysis of massive multi-sources heterogeneous sensing information. Portable novel alarming devices are used by workers in the crossing passage construction, so that the real-time risk warning signals can be sent to the workers in the construction site by means of sound, light and vibration. The integration of the sensing, transmission, analysis and controlling of the construction safety of the metro-tunnel crossing passage under Yangtze River is realized. This paper provides a scientific and reliable method for real-time construction safety controlling of the crossing passage under high water pressure conditions, and it is of value in theoretical analysis and engineering application.