Wireless sensor network for monitoring transport tunnels

A hybrid wireless sensor network has been developed for structural monitoring of transport tunnels. The system combines the advantages of wired and wireless sensing to simplify and speed up installation. The wireless modules are based on low-cost sensors for inclination or displacement, and temperature and humidity. These are combined with a commercial radio module to eliminate the need to install cables around the tunnel. The modules report readings back to a gateway installed on the wall of the tunnel, automatically relaying the readings from other modules as required. The readings are transmitted to the surface along cables that can be quickly and easily installed in the cable trays running along the walls of the tunnel and up the closest vent shaft. From the surface the readings are sent to a server via the mobile phone network and made available in real time on a web page. The results of a trial installation on the London Underground Jubilee line are reported.