MONITORING ON THE ARCH RINGS DEFORMATION IN THE NO.3 TUNNEL OF BAINIJING WITH BOTDR BASED STRAIN MEASUREMENT TECHNIQUE

This paper presents an application case of fiber optic sensor in the Structural Health Monitoring of tunnels.In the No.3 Tunnel of Bainijing in Yunnan Province,BOTDR was applied to monitor the arch rings.According to the geological condition of the tunnel,ten arch rings were selected at the end of the tunnel and fiber optic sensors were installed in them.In the following whole year,the strain distribution of these cross sections was recorded.The monitoring results showed that these ten arch rings retained stable in the monitoring period except the arch ring at the alignment of K84+508.2,where the surface of lining expanded in rainy season.It was believed that the rain infiltrated into the soil and increased the pressure of the adjacent rock mass,and then the arch ring was crushed to deform.