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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.

Controlling building displacements induced by tunnelling is a major issue in densely urbanised areas, particularly for listed heritage structures. Major tunnelling projects provide opportunities to assess the ability of advanced numerical models to address this issue, in conjunction with the large amount of monitoring data that are gathered during the works. This paper considers the case of two Grade-I listed buildings (St. Mary Abchurch and Mansion House) affected by the Bank Station Capacity Upgrade in London (UK) where complex excavation works were conducted to improve the existing underground infrastructure. Both conventional and innovative monitoring was carried out to control the effect of tunnel construction on these buildings. Following the works, three-dimensional finite element analyses were conducted by adopting a semi-coupled modelling approach. In these analyses, the pre-existing damage in the buildings prior to tunnelling has been considered by adjusting the properties of embedded solids that are used to idealise the structure. The analyses also considered salient aspects that are often neglected in routine risk-assessment procedures, such as the excavation modelling sequence covering both pilot tunnelling and enlargement, the skew building-tunnel alignment, and the effect of closely spaced tunnel excavations on surface ground deformations. The results highlight the challenges associated with idealising historic structures with semi-coupled models; nevertheless, they encourage the integrated use of innovative monitoring systems and advanced numerical modelling as a tool to control the process of tunnel excavation in complex urban environments.

Detailed site investigation and monitoring data gathered during underground construction projects creates an opportunity to evaluate and improve the techniques used to model the influence of tunnelling on existing buildings. This paper discusses the application of the semi-coupled modelling technique to two historic buildings affected by the construction of new tunnels for the Bank Station Capacity Upgrade in London, UK. Using the semi-coupled modelling approach, the buildings were idealised as equivalent elastic anisotropic solids, while high fidelity models were used to model nonlinear behaviour of the soil and tunnel excavation process. These analyses highlight the flattening of displacement profiles, and the important influence of tunnel advance on skew facades. However, comparison of modelling results to levelling data, highlight some limitations of using equivalent solid models to represent masonry buildings.