Soil nails are a slightly different technology than traditional helicals. The main difference is the configuration of the lead section. Instead of the helical plates on the lead section increasing in size (8” 10” 12”), they remain constant. An 8” helix will be followed by another 8” (24” apart, 3X the diameter of the lead plate). Extensions will be used to advance the nails beyond the failure plane, typically to a depth equal to 75% of the height of the wall, but this can vary based on soil conditions.
Helical Soil Nails are similar to grouted soil nails. They are site-specific, but, with the right soil conditions and loads, are superior to grouted soil nails and can be a welcomed alternative. This is due to no spoils, fast installation, access mitigation, elimination of staging issues, quick and easy mobilization, immediate loading, and cost considerations. Smaller crews translate into reduced labor and costs on most projects.
Helical soil nails are a shotcrete wall and an alternative to soldier beam and lagging. They are used in combination with wire mesh and shotcrete to secure the face of the wall by anchoring the wall well beyond the failure plane in suitable soil, eliminating any further deterioration. The following are a few case studies illustrating site specific situations where helical soil nails proved to be the preferred fix.
Catskill Aqueduct Project
This seventy-five mile-long, on-going project spans five counties and nineteen towns in New York State. Helical soil nails were used in a slope stabilization in Yorktown Heights, NY, adjacent to residential homes, to access aqueduct manholes. This challenging job involved tight access, mobilization restrictions, and adjacent private property concerns.
Catskill Aqueduct Repair & Rehabilitation – Danbro Distributors
Pepsi Production Plant
Another slope stabilization project, but this one involved a busy service road and parking lot which needed to be supported to facilitate new construction.
Pepsi Production Plant – Danbro Distributors
Poplar Point Pump Station
This project involved excavation and slope stabilization in furtherance of new construction at a utility facility for a pump station project. The new construction could not proceed till the slope was stabilized and helical soil nails were the quickest and least intrusive solution.
Poplar Point Pump Station – Danbro Distributors
Greenwich, CT Residence
Helical tiebacks, as well as helical soil nails, were used on this challenging residential project. Speed of installation, same mobilization for both earth retention systems, and varying soil conditions drove the decision to use helicals.
Greenwich, Connecticut Residence – Danbro Distributors
WB&A Trail
This project originally involved traditional excavation methods – soldier piles and lagging with helical tiebacks – replaced with an innovative helical soil nail alternative to overcome overhead restrictions.
WB&A Trail – Danbro Distributors
Many of the typical advantages of helical technology are at play in slope and wall stabilization projects. Helical soil nails mitigate or eliminate issues such as access, spoils, cure time, staging, and mobilization by using less equipment than grouted tendons. Smaller crews translate into reduced labor and still further cost mitigation. Helical soil nails are site specific but can be a welcome alternative for contractors and professionals when site conditions or costs are an issue.
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