Wireless sensing on shield tunnels in Shanghai

Recent years more and more shield tunnels are being used in urban critical infrastructure in China, such as road and metro tunnels. Its safety during the construction and operation should be most crucial. Monitoring the tunnel behaviour including deformation, water leakage, crack and damage, etc. is an effective way to control the lifetime safety of shield tunnel. In this paper, a “smart” sensing system coupling the tilt sensor, seepage sensor, and crack sensor with MEMS-based and Zigbee-based mesh network and their application in road and metro shield tunnel are firstly proposed in China. All these sensors were developed and validated by indoor model test for shield tunnel segmental lining structure. MEMS tilt sensors were installed in 2 sections of the Shanghai Dalian road shield tunnel with 11 m outside diameter and 480 mm segment thickness. Tilt, seepage and crack sensors were installed in one interval shield tunnel in Shanghai metro with 6.2 m outside diameter and 350 mm segment thickness. The lateral convergence transferred from tilt sensor, area of seepage, opening and closing of joints can be obtained by WSN. Both measured data shows their stable and reliable. The merit of this system, compared to the conventional monitoring system, is its ability of real-time dynamic monitoring regardless of the running of road or metro tunnel.