Strand Anchors allow unobstructed Travel on Highway 63
Canadian Highway 63 crosses the province of Alberta from North to South, through the Athabasca oil sands region near Fort McMurray. Due to the growing oil sand industry, the two lane road had become increasingly overloaded and was expanded by the addition of two lanes in 2006.
In one of the sections of Highway 63 that runs through one of Canada’s largest mining areas, long term slope movement was identified. As a result, the owner decided to carry out slope stabilization measures simultaneously with the widening of the section.
During the geotechnical analysis, a deep failure zone was detected on both sides of the highway that had to be stabilized using permanent anchor walls. Due to the steep drop off of the slope, the owner decided to use Double Corrosion Protected (DCP) DYWIDAG Strand Anchors as proposed by DSI. In fact, the installation and coupling of strand anchors in steep terrain is safer than the installation of bar anchors.
DSI had especially adapted the strand anchors to the extreme weather conditions and also supported the contractor during the onsite tests carried out on the anchors. DSI supplied load cells for the tests to collect the data necessary for fine tuning the anchor forces.
The anchors had to be bonded through three different overburden zones into the prevailing limestone. Since soil conditions along the complete anchor wall were non homogeneous, and the limestone in the soil varied in elevation by up to 7m, it was very difficult to accurately predetermine anchor lengths. Due to the depth of the failure zone, especially long anchors with free lengths ranging from 16 to 31m had to be used.
Initially, the strand anchors were installed at the east side of the Highway. Afterwards, the drilling and installation work was carried out at the three rows of soil anchors on the western wall. All in all, 578 4-0.6" and 12-0.6" DCP DYWIDAG Strand Anchors were installed, tested and tensioned using jacks provided by DSI. The anchors were installed into Ø 225mm boreholes and had design loads ranging from 630kN to 1,180kN. In order to provide additional corrosion protection, the ground anchors were post grouted and fitted with anchor caps at the upper ends.
Despite the difficult access and the fact that work had to be carried out in unfavorable weather conditions during the winter season of 2010/2011, the contractor was able to successfully complete the installation of the ground anchors.