SGG Lunch Presentation: Settlement Analysis and Monitoring of Approach Fills for the 50th Street Grade Separation Project in Edmonton Alberta

Event Summary

Serving as a key north/south arterial road in Edmonton, 50 Street functions as both a major goods movement and commuter corridor. The existing at-grade Canadian Pacific Kansas City Limited (CPKC) railway crossing presented a major bottleneck to traffic movements, resulting in significant delays for the travelers.

To alleviate congestion and improve traffic flow, the 50 Street widening and grade separation project involved constructing an approximately 70 m long overpass over the railway crossing, with Mechanically Stabilized Earth (MSE) Wall-supported approach fills up to 11 m high, widening 50 Street to three lanes in each direction.

A comprehensive geotechnical investigation and PLAXIS 3D finite-element settlement analyses were completed to assess subsurface conditions and predict short- and long-term settlements under staged construction. Wick drains were installed beneath higher sections of the approach fills to accelerate the embankment settlement. A geotechnical instrumentation program was implemented to monitor the performance of the MSE wall fill placement.

The instrumentation data provided real-time feedback, allowing continuous evaluation of foundation behaviour and confirmation of design assumptions throughout construction. The measured settlements generally agreed with the estimated settlements by the 3D numerical analyses, supporting the design and construction methodology for the overpass.

Presenters

Mark Gallego, M.Eng. P.Eng., and Tamer Elshimi, Ph.D., P.Eng., from Thurber Engineering Ltd. in Edmonton, Alberta.