I have written extensively about the use of helical anchors as an alternate to grouted tendons for tiebacks and soil stabilization. As is typical with helicals, considerations are site, soil, and situation specific. Click here to read The Use of Helical Anchors for Tiebacks.
Helical Anchors have become an increasingly popular alternative to drag or deadman systems for bulkheads. A recent project I visited in Manahawkin, NJ illustrates the reasons why.
EZ Docks, a marine construction company in Ocean County, NJ had completed the replacement bulkhead on the east side of Yacht Basin Marina in Manahawkin last year and was returning to complete the west side. According to Billy Crow, the Project Manager for EZ Docks, the challenges were obstructions: old tie rods, abandoned electrical wires, and 200’ of sewer line running parallel to the bulkhead. A total of 88 anchors were installed with 2 walers – approximately 20’ deep on a 35⁰ angle to avoid the sewer line. The helical anchors eliminated both the increased risk of potential damage to the sewers and a deeper excavation for the trench that would have been necessary if using a deadman system.
The soil in marine environments in Ocean County varies from hard deadpan sand to WOH marsh mud. Soil conditions can even vary on the same job. Marine Lumber & Piling, who supply IDEAL helical anchors, often suggest that their helical customers use a combination of longer and shorter extensions, so that they don’t waste steel and money when achieving the depth dictated by the required torque. In this case, the required torque was 3,000 Foot Lbs. In addition to 7’ leads and 7’ extensions, Marine Lumber sent a bundle of 3.5’ extensions for use when the torque was achieved at a shallower depth. It came in handy as the final depth varied between 17’ and 22’. Click here to read the Yacht Basin case history.
Danbro supplies Marine Lumber, a rare customer reseller, with their helical anchors. This provides convenience for the Installer who can “one stop shop” all of their bulkhead/marine supplies from one source, Marine Lumber. “It cuts into our profits a bit, but it makes sense and better serves the customer,” stated Frank D’Angelo, Danbro President. Danbro provides the same level of customer support to all of our customers, even those “once removed”! In fact,it was Danbro who recommended the “All Torque” digital torque indicator to EZ Docks to simplify the process and produce the popular electronic read-outs. “The inspectors love the print outs,” said Billy, “as it makes their job easier.” Click here to access Marine Lumber & Piling website.
IDEAL’s contribution, however, may be the most significant. The SS 150 provides more torque than the lower capacity SS 5, so obstructions on site and dense sand are easier to push through. Billy indicated that he “couldn’t be happier” with this product as he has been on many jobs where the extra torque was necessary to achieve the depth or to fight through trash. He also indicated that helicals have almost completely replaced drag or deadman for replacement bulkheads. “Homeowners often have patios, pools, or landscaping that would be ripped up, destroyed, or in the way if we didn’t use helicals for tiebacks,” stated Billy. Click here to access EZ Docks: New Jersey & Florida Floating Docks Website.
The rationale for using helicals for a variety of applications in marine environments is detailed here and supports EZ Docks’ observations.
Click here to read Engineered Foundations for Coastal Infrastructure: Meeting Design Challenges in Marine and Littoral Environments
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