Case Study: Automatic Reflector-less Surface Deformation Monitoring of a 21-lane Highway during SEM Tunneling Construction

ABSTRACT: In underground construction, geotechnical monitoring allows the instant evaluation of the performance of the work and contributes to maintaining public safety in the project’s environment. Automatic Motorized Total Stations (AMTS) provide automatic, high precision and near-real time monitoring of the ground and of surrounding structures. This paper introduces AMTS in reflector-less mode, to monitor ground deformation during a Sequential Excavation Method (SEM) tunneling project in Canada. The Highway 401 and 409 Rail Tunnels project requires continuous near real-time monitoring of nearly 500 points across a 21-lane highway with no interruption of traffic. This paper explains the workflow of RTS in this context. The authors focus on the specifics of the design of this unique reflector-less monitoring program and on challenges addressed during its implementation and maintenance. The paper is aimed to confirm the relevance of RTS in reflector-less mode for tunneling activities in urban areas.