Ottawa Light Rail Transit is a 2.4-km-long two-track running tunnel and Rideau underground station. The tunnel is 10 m wide between spring lines with its crown between 12 and 26 m below ground surface. The tunnel was driven in the local Verulam and Lindsay sedimentary rock formations, with parts completely in soft ground of glacial till. Emad Iskander, Ph.D., PE served as the Structural Design Engineer and Engineer of Record for this project. The Sequential Excavation Method (SEM) construction was performed by road headers and supported by glass fiber reinforced plastics (GFRP)-reinforced initial shotcrete lining and rock bolts. The Rideau station is 20 m wide between spring lines and 12 m below ground surface, partly in soft ground and the rest in the Verulam rock formation. In addition to the two tracks, the station housed a center platform and a concourse slab. The cavern was excavated by road headers and excavators and supported by a thick shotcrete lining after stabilizing the roof by a pipe umbrella. A domed shotcrete headwall closed the cavern’s west end and connected to the running tunnel in the soft ground reach.

The structural design of both units was based on 2D finite element analyses for the typical sections and 3D analyses for station parts that were connected to other elements such as access shafts, escalator tunnel or other utility adits or niches. Complete construction documents including drawings, design reports and specifications were delivered to the contractor for construction. In addition, several on-site construction issues were addressed during site visits.