Using an innovative method combining earth anchors and shotcrete, foundation contractor Schnabel Foundation Co., Cary, Ill., temporarily shored a deep roadside excavation. Earth on one side of a quarter-mile stretch of the roadbed was about 25 feet above the proposed grade. Normally, excavating such a hill down to grade would require the use of sheet piling or soldier piles and lagging to shore the embankment until a permanent retaining wall could be built. But Schnabel determined that it could do the job more cost effectively by using earth anchors and shotcrete -- a method the contractor had used successfully on other projects.
Schnabel performed the excavation and shoring work in 5-foot increments down to grade. After making the initial 5-foot cut, workers used a track drill to bore holes into the embankment for the earth anchors: 1-inch-diameter high-tensile-strength threaded rods, epoxy coated to prevent rust and corrosion. Plastic spacers centerrf the rods in the holes. After installing the rods, workers pumped a cementitious grout into each hole to hold the anchors.
When all the rods in a given area had been placed, wire mesh was hung on the rod ends extending out from the embankment. Next, #4 rebar were placed horizontally across the anchor rods to serve as additional reinforcement. After workers installed all the anchor rods, reinforcement and drains, they sprayed wet-mix shotcrete onto the prepared area to a thickness of up to 12 inches.