Deformation Monitoring of Shield Tunnel Based on Distributed Optical Fiber Strain Sensing Technology

Abstract

n this paper, a deformation monitoring method for shield tunnel based on distributed optical fiber strain sensing technology is addressed. Firstly, a novel distributed optical fiber strain sensing technology based on pulse-pre-pump Brillouin Optical Time Domain Analysis (PPP-BOTDA) was introduced, including the packaging process and deployment methods of corresponding optical fiber sensors. Then, the relationship between structural distributed strain and longitudinal settlement was deduced based on the longitudinal equivalent continuous model of shield tunnel. Finally, a model experiment of Nanjing Yangtze River Tunnel was conducted to study the longitudinal deformation property of tunnel under locally even loads with the distributed optical fiber sensors. Experimental results show that the distributed strain measurement can reflect distribution of tunnel’s longitudinal deformation, based on which, the structure damage can be detected precisely. It is also shown that the tunnel’s longitudinal settlements derived by the proposed method agree well with those measured directly with the traditional displacement meters. Efficiency of this method is thus validated.