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Grierson Hill

January 21, 2018

Doublestar Drilling (DSD) was awarded the design build contract to provide the temporary shoring for Support of Excavation (SOE) on Grierson Hill for the North Portal tunneling and construction for the Valley Line LRT in Edmonton, AB with TransEd Corporation.

DSD was selected to provide an engineered solution for the temporary shoring for the excavation that met stringent project requirements, while ensuring the footprint of this specific scope of work allowed for the other construction activities, including the permanent global slope stability works, tunnelling activities and LRT bridge construction. Due to the geometry of the existing hill and excavation along with the minimal area to complete this shoring work, a shotcrete and soil anchor shoring design was selected by DSD and Engineer by Tetra Tech Canada Inc.

DSD worked with TransEd to provide an economical contractual solution that utilized certain resources and procurement opportunities with TransEd. For example, materials that were surplus ordered by the Contractor in other areas of the project were used and incorporated into the design strategically to minimize the overall construction cost to the Owner.

Grierson Hill has a total of 21 vertical rows of Soil Anchors with a total of 681 Soil Nails to be installed on all three SOE walls. Due to the Project Agreement requirements, the Soil Nails were exceptionally long, averaging 18.0m in length in order to meet performance requirements of deflection and movements. In addition to the Soil Anchors, DSD will also apply over 1000m3 of 150mm thick high strength Shotcrete to the face of the SOE as part of the shoring design and stabilization.

Currently DSD has dedicated two specialized anchor drills rigs, a Soilmec SM14 (top image) and an excavator mounted TEI HEM-1000 seen in the picture above in order to work on the challenging hillside and footprint, minimizing any additional site works or benching required for the anchoring equipment. Because of the overall excavation depth of the SOE shoring system, Soil Anchors were drilled and bonded into four distinctly different soil types at times. A detailed soil anchor testing program has been implemented to test each soil type and strata, to validate assumed anchorage bond values through verification and performance testing.

DSD’s experience and versatility continue to prove invaluable to the success of the Valley Line LRT shoring and piling requirements. The partnership between TransEd and DSD has now lead to multiple safe, effective, and efficient projects.