Planning the monitoring required to confirm the movement and rotation of tunnels and trackwork due to excavation and tunnelling

Two interchange stations at Outram Park and Dhoby Ghaut Stations are to be constructed along the proposed North-East Line. The construction of these two interchanges involved station excavation and tunnelling near to and under the existing MRT tunnels. To assess the effects of the work on the existing tunnels, ten limit states’ were established, with respect to structural integrity and track alignment. This paper describes the instrumentation used to check against the ten ‘limit states’, and discusses the assessment and reporting of the data.