A Fibre-optic Strain Measurement System to Monitor the Impact of Tunnelling on Nearby Heritage Masonry Buildings

Fibre-optic sensing technologies provide the opportunity to measure detailed structural response in real time over long durations. This paper describes a first-of-its-kind application of Fibre Bragg Grating (FBG) measurement to monitor the impact of tunnelling works on two Grade-I listed buildings in London, UK. After describing the principles behind the strain sensing technology, laboratory tests are discussed. These tests are used to calibrate strain sensors and validate the newly developed temperature compensation technique. The arrangement of sensors and their installation on the buildings is then presented. Fibre-optic temperature and strain measurements from the ensuing three-year monitoring period are compared with other independent measurements. It is demonstrated that the system enabled direct real-time monitoring of both the short- and long-term impact of tunnelling on the historic assets in a reliable manner.