Beyond the Build

Construction Trends

Soil Nails for Tough Sites

Soil Nail 2

Someone once said to me, “Most of the good sites are taken.” While I’m not sure this is exactly true, the last few decades have given us new techniques for “challenging” soils, adding new tools to our toolbox. Previously un-developable sites can now be developed in a cost-effective manner.

Over the last few years, we have used one of these tools–soil nails–in the Southeast. The process is fairly simple. The soil nailing technique involves “sewing” the exterior surface to the face of an embankment to stabilize it. Crews insert relatively slender reinforcing elements into the slope, then grout them into place. With our projects, we then use reinforced shotcrete for the surface application tied into the soil nail head plates.

It’s effective, but I won’t say soil nails will win any beauty contest.

We recently used soil nails on a tough site to eliminate the sloughing of material and stabilize the surface. I’ve seen similar applications in the mountains to hold back loose material like rock. The surface for stabilization is flexible mesh in lieu of shotcrete.

Here’s what we’ve learned on our projects:

  • The underlying soil has got to have some ability to stand unsupported prior to soil nails. The technique is to stabilize the surface for long-term containment.
  • The soils need to have some cohesion ability and be free of boulders, corrosive soils and fine-grained soils. It also helps when the soil nails are not subject to constant freezing temperatures freeze/thaw cycles.
  • Ensure that the groundwater table is below the bottom of the wall.
  • Soil nails work very well in tight working conditions. Smaller equipment, relatively rapid installation and fewer materials.

Overall, we’ve found soil nailing very cost-effective, given the right circumstances. If the look is not exciting, you can cover it up. On one of our jobs, we had English ivy planted to cover the wall and no one knew the skin.

Any experience using soil nails?

Merrill Stewart Jr.

Merrill Stewart is Founder and CEO of The Stewart/Perry Company, a commercial building contractor based in Birmingham.