Ground Anchors Stabilize Highway Bridge Abutments

Calgary\u27s Glenmore Causeway, constructed in 1962 across the Elbow River, consists of an earthfill embankment with a waterway spanned by a 43 m long bridge, the abutments of which are supported on spread footings founded in the embankment fill. Between the 25 m deep sand and gravel embankment fill and the sub-horizontal bedrock surface is a compressible clay layer up to 5 m thick. To improve abutment stability during peak river flows, 126 post-tensioned Dywidag ground anchors up to 60 m long were installed through the concrete slabs armouring the abutment slopes. Twenty-two anchors were terminated in the embankment fill and the rest were grouted into bedrock. After a series of lift-off tests and anchor retensioning to compensate for ground consolidation, a procedure for predicting the rate of anchor load relaxation was developed. It was concluded the anchors are performing satisfactorily although periodic re-tensioning will be required