A new photogrammetric system for high-precision monitoring of tunnel deformations

A new photogrammetric system has been developed to monitor tunnel deformations with high precision. The system fundamentally applies digital image correlation techniques to process images. It is digital in nature and is compatible with the industry's vision of moving towards the smart and digital monitoring of existing assets. It has been installed successfully within the London Underground railway and a number of other tunnels to demonstrate the potential of remote deformation monitoring of such assets using off-the-shelf cameras. The system is able to measure deformations with precisions higher than 0.1 mm, enabling the monitoring of sensitive deformations such as imposed curvatures. This paper highlights the application of photogrammetric systems in monitoring the deformation and condition of assets in real time and highlights the advantages that such systems bring. A case study has been chosen to demonstrate these. The case study is the monitoring of an escalator barrel in Moorgate station in London that was influenced by a sprayed-concrete-lining excavation directly underneath for the new Elizabeth line.