An Innovative Approach to Spillway Weir Stabilization Utilizing Underreamed Drilling Methods Adapted from the Oil Industry

Failure of traditional friction anchors at low capacities in high plastic clay shales resulted in an innovative solution by drilling an underream in the anchor bond zone using drill tools adapted from the oil industry to ensure a stabile spillway. This technical paper will detail the associated challenges and successes of an anchor study program and production anchors utilizing an end bearing anchor in lieu of the traditional side friction anchor, a technique not practiced in post tensioned anchor installation in over 30 years.