Constructability Issues Associated with Long Ground Anchor Installation on Large Soldier Pile Walls and Possible Mitigation Measures: Case Study Peregrine Slide and Westport Slide Complex-PPT Presentation

PPT Presentation

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The presentation examines constructability challenges associated with long ground anchors in large soldier-pile retaining walls, using California’s Westport Slide Complex and Peregrine Slide projects as case studies. These walls used anchors up to 230 feet long, with design loads as high as 300 kips and drilled-hole diameters of up to 8 inches.<br /><br />A key challenge is anchor interference. At Peregrine, piles were spaced only 7 feet apart, while anchors extended 230 feet. Routine drilling tolerances of about 2 degrees can cause adjacent anchors to cross; tighter tolerances require specialized methods. Mitigations include alternating drill angles between piles, controlling angles carefully when starting holes, and setting drills perpendicular to the surveyed wall line rather than relying on potentially misaligned piles. Increasing pile spacing may help, but can create lagging-span concerns.<br /><br />Long anchors can also be difficult to insert. Anchors may kink when forced into holes, increasing friction and causing measured elongations to fall below theoretical values—potentially nearing the 80% acceptance criterion. Steeper inclinations, around 20 degrees, can ease installation, though they reduce horizontal resistance. Properly placed centralizers and thorough hole cleaning also help anchors slide in straighter and reduce friction losses.<br /><br />High factored test loads require more tendon strands and larger holes. An 8-inch hole is substantially more demanding to drill than a 6-inch hole, requiring specialized equipment. Loads around 300 kips may trigger the need for larger holes, depending on soil conditions. The presentation recommends coordinating with designers to keep loads below 300 kips, with roughly 260 kips as a useful target when 6-inch holes are desired.

Keywords

long ground anchors

soldier-pile retaining walls

constructability challenges

anchor interference

California Westport Slide Complex

Peregrine Slide project

drilled-hole diameters

design loads

anchor installation

centralizers