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Fountain Slide Design-Build Track Mitigation Project

Fountain Slide Design-Build Track Mitigation Project
Date: 2016

The Fountain Slide is part of an ancient earthflow which impacts both a portion of a railway owned and operated by Canadian National as well as public Highway No. 99. The impact on the railway was increasing and leading to operational challenges. AGRA and Nicholson Construction was awarded a design-build contract following a Request for Proposal (RFP) process to install a solution to improve the slope stability to a safe margin. The rate of slope movement at the time of mobilization was in the range of 3 to 6 mm per day as measured at the location of an existing beam and lagging retaining wall supporting the railway bed.

Solution:

A two-part solution was employed to arrest the slide movement and improve the global slope stability factor of safety. The first part of the solution involved the installation of battered and fully grouted micro piles. These piles acted as ductile shear piles having the potential to bend and possibly even shear given the rate of slope movement during the installation process. The second part of the solution involved the installation of passive anchors through the existing retaining wall and connected by a cast in place concrete waler. In addition to the micropiles and anchoring work, a considerable amount of controlled earthworks was required to establish site access and maintain safe working platforms. Ongoing slope monitoring during the execution of the work was accomplished using slope inclinometers and real-time surficial monitoring using a CYCLOPS integrated survey network.