Monitoring a heritage building restoration project with geotechnical instrumentation

Infrastructure projects have been undertaken, including major work to modernize, both structurally and esthetically, the 150-year old West Block Building in Ottawa while maintaining its heritage appearance. The project required extensive monitoring with geotechnical instrumentation. The structural work requiring instrumentation had three phases, backfilling of abandoned tunnels, excavation of the inside of the north wing to add new basement floors, and excavation of the inner courtyard to add new basement floors. There are several limitations that were to be overcome during installation. The line and sensors had to be installed in cramped spaces, around beams, inside doorframes and so on. The complex arrangement in the building made it impossible to avoid curves that could trap air bubbles in the liquid, so the line had to be filled before being attached to the wall. To minimize inaccuracy due to temperature changes in the liquid and to have access to the full measurement range, these settlement measurement systems also require that the sensors be at the same elevation, within 10 mm of each other. When monitoring an already existing structure, a long enough baseline will allow engineers to work out the relationship between temperature and tilt and thus enable the analysis of all subsequent data acquired during the project.