Installation Methods for Nails in Soil Nailing Walls
In the United States, nails (or soil nail reinforcements) are mainly installed using the drill-and-grout method. Other techniques are briefly described below.
Types of Nail Installation Methods
1. Drill-and-Grout Nails
Boreholes, typically 100–200 mm in diameter, are drilled in the foundation soil at about 1.5 m spacing. Steel bars are placed first, then grout is injected. Drill-and-grout nails are the most common type used in soil nailing walls, suitable for both temporary and permanent walls (if proper corrosion protection is provided).
2. Driven (Displacement) Nails
These nails are relatively small in diameter (19–25 mm) and are pushed directly into the soil. Spacing is about 1–1.2 m. Installation is faster than drill-and-grout, but corrosion protection is poor. Therefore, they are mostly used for temporary walls.
3. Self-Drilling Nails
Hollow steel bars allow drilling and grouting in one step. Grout is injected through the hollow bar during drilling, filling the borehole from top to bottom. Rotary-percussive drilling is used. Faster than drill-and-grout, and partial corrosion protection is provided by the grout. Common in temporary walls.
4. Jet-Grouted Nails
High-pressure grout is used to drill and advance the borehole to the final depth. Grout protects the steel from corrosion. In the second step, bars are typically installed using percussive-vibratory drilling.
5. Launched Nails
Bare steel bars (19–25 mm diameter, ~8 m long) are fired into the soil at high velocity using compressed air. This allows very rapid installation with minimal site disturbance, but controlling nail penetration depth can be difficult. Used only for temporary walls.
