Identification of water ingress in brick walls to aid preventive maintenance

The research explored the role of thermal cameras in preventing water ingress in brick-lined tunnels.

Water ingress in metro tunnels causes many problems, such as signal failures and corrosion of support structures. These cause delays in the service, leading to loss of revenue. A system that could detect when water enters a tunnel would help to create scheduled maintenance plans rather than reactive maintenance.

To test thermal camera performance, a pipe system was installed, allowing water to enter the back of a model brick wall. Both thermal and normal photographs were taken. Thermal images were far clearer than normal photographic images, which only detected colour change when the area was very close to saturation.

After analysing the moisture content of the bricks, images were reanalysed using a software algorithm to plot saturation levels. These results were applied to thermal surveying of tunnel TL57, on London Underground’s District Line. They showed areas with saturation levels above 80%, indicating significant moisture in the bricks’ pores. This suggests the tool could be used in other structures where water ingress damages performance and increases decay patterns, allowing scheduling and budgeting for preventive maintenance and reducing reactive maintenance costs.

The research explored the use of thermal cameras to measure saturation levels in London Underground’s brick tunnel linings. This technology has the potential to identify areas needing maintenance to prevent water ingress, particularly around electronic equipment that controls trains. This would reduce both disruption and revenue loss for London Underground.