The Calgary Airport Trail Tunnel is a cut-and-cover, two-cell roadway tunnel constructed under the
Calgary International Airport’s runway and three associated taxiways. It is owned by The City of Calgary (The City) and is on land leased from the Calgary Airport Authority (YYC). The structure is a cast-in-place, conventionally reinforced concrete rigid frame on spread footings with two spans of 17 m each and a total length of 620 m. The Tunnel was designed according to the Canadian Highway Bridge Design Code (CHBDC). One of the load cases considered in the design was loading due to temperature effects (including temperature variations and thermal gradient). Based on the CHBDC , the design temperature range for Calgary is from -34 to 38°C. It was discussed during the design stage that the Tunnel, which is a buried structure, may not actually be subjected to this temperature range. The design team could not find any references that addressed temperature ranges inside tunnels.
Another issue raised during the design stage was the necessity for movement joints. Although some references recommend joints as close as 9 m apart, there are tunnels that have been constructed without any joints. To investigate these questions for future designs, it was discussed with The City and it was agreed to put temperature and movement monitors in the tunnel. Wireless sensors were cast into the concrete walls and roof slab at 40 locations to measure temperatures at two surfaces and the mid-depth of each section. Also, surface mounted sensors were installed at two movement joints to monitor the tunnel’s movements.
After providing a summary of the Tunnel and monitoring design, the paper emphasizes the findings from the monitoring program, including:
· Average maximum and minimum temperatures and thermal gradients recorded inside the
· Comparisons with temperatures recorded outside the Tunnel at the Calgary Airport
· Comparisons to the design temperature range and gradient provided by CHBDC 
· Results obtained from movement sensors.