Stable Solutions in an Area prone to Landslides: The Peace River Project

The Peace River Project is a slope stabilization project that was recently carried out near the Canadian town of Peace River in Northwestern Alberta. The Peace River lowlands are a historically active landslide area: Every year, nearly half of all the slides in the Province of Alberta occur here. Since Highway 744 was opened to traffic in 1985, 14 landslides in this area have had to be stabilized using various methods.

In May 2013, a large landslide occurred on Judah Hill and closed an important section of Highway 744. A large scale rehabilitation project began that required the construction of three cast-in-place (CIP) pile walls. The CIP pile walls vary in length from 40m to 120m and are topped with a concrete cap beam.

Lateral support is provided by a total of 519, 32mm Ø double corrosion protected (DCP) DYWIDAG Soil Anchors having a weight of 142.34t. The soil anchors supplied by DSI Canada were installed in the concrete cap beam as well as through the center of each of the 1.2m diameter piles. Additional anchors with bond lengths of 12m were installed through some of the CIP piles, at angles varying from 25 to 32 degrees from horizontal. Total tendon lengths from 35m to 58m were required in order to reach the competent, very stiff clay till layer beneath the landslide slip plane surface.

The design lock off loads for the DYWIDAG Soil Nails varied from 162kN to 272kN. Several vibratory wire load cells were also installed with the soil nails for permanent load monitoring at each pile wall. The DYWIDAG DCP Soil Anchors were injected with cement grout following installation.

Work had to be carried out within a very short time frame in order to be able to reopen the important federal Highway 744 as soon as possible. DSI worked closely with the drilling subcontractor to ensure timely delivery of the soil anchors and the necessary testing equipment throughout the project.

Despite severe cold weather conditions during the winter of 2014, the project was successfully completed and the road quickly reopened to traffic. The new pile walls will provide a safe and efficient connection of the town of Peace River to the region.

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Alberta Transportation, Canada