Monitoring the behaviour of an existing royal mail tunnel: London underground bond street station upgrade works

The response of existing tunnels to adjacent new tunnelling works is an area of special interest to both civil engineering designers and tunnelling engineers as well as asset owners. Field monitoring is critical as it provides vital data about the response of the existing tunnels that informs future design improvements. This paper focuses on the response of the existing, near century-old royal mail tunnel in the vicinity of bond street London underground station in London, UK. Cambridge's 'Centre for smart infrastructure and construction' (CSIC) deployed various state-of-the-art instrumentation systems to investigate the behaviour of the existing royal mail tunnel during the construction of a new passenger tunnel as part of London underground bond street upgrade scheme. The instrumentation includes distributed fibre optic strain sensing (DFOS), photogrammetry and strain gauge instrumented tunnel bolts. The monitoring systems combined were able to provide a very good insight into the existing Royal Mail tunnel behaviour, as the construction of the new tunnel beneath was undertaken