Masonry Magazine October 2010 Page. 33
Retaining Wall Project
The project involved drilling anchor bolts into the cliff face and filling the space between the cliff and the geogrid with compacted backfill behind the geogrid. Then a steel bar was attached to the anchor bolts and the geogrid attached to the steel bar to secure the wall to the cliff face.
"Greg was careful about the drilling," says Andrassy. "He made sure he had plenty of depth, and in a lot of cases he probably over-drilled them. It was a pretty conservative design. Since you're dealing with some unknowns and with the nature of the rock - hard, competent rock to more crumbling rock - you've got to err on the side of caution."
The existing seawall was used as the footing. The concrete wall extends upward for 17 feet and an 18-inch cap on top rests on a ledge chiseled out of the cliff face. The Versa-Lok wall rests on top of the cap. The seawall required about 600 cubic yards of concrete.
Once the footing was completed, a series of three decks was built that jutted out from the cliff and was connected to a pier on the water by zig-zagging stairways. The retaining wall was built behind the deck/stairway structure.
The Versa-Lok wall begins at about 13 feet above the water level. It's 65 feet wide and 27 feet tall, and was built in three tiers with a slight curve.
"That allowed us to follow the bluff face," Andrassy says. "The nature of the bluff face was such that the lower two-thirds were very steep, nearly vertical. The rock transitions to soil at the top, so it starts to fall back. That allowed us to bench into the existing face, so each segment has its own footing."
About 3,000 Versa-Lok Standard units in a blended pattern of 80 percent brown and 20 percent gray were used. A special conveyer belt system was designed to lower the blocks down the cliff face one by one; a chute alongside the conveyer was used to transport the backfill aggregate.
"The higher we went with the wall, we had to adjust our system of transport," says Andrassy. "We had a little innovation going on. Everyone got a good workout. No matter how good you are at moving it, that's a lot of block."
"With its flexible slot-and-hole pinning system, Versa-Lok was perfect for the application," says Norton. "One of the biggest challenges of the job was explaining to people what it was going to look like when it was done. The other big challenge was getting the material down there. But I like the challenge. I don't like cookie-cutter designs."
This was definitely not a cookie-cutter design, and it may not be the last such wall he designs, says Andrassy.
"There are all these million-dollar houses up here and none of them can get down to the water," he says. That may change once the neighbors see this wall. IMAS
The Versa-Lok manufacturer was 4D/Schuster's, Sheffield Village, Ohio. For more information on Versa-Lok Retaining Wall Systems, visit www.versa-fok.com or call 800-770-4525.
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