Soil Nailing

Soil nailing is a technique for reinforcing, stabilizing and retaining excavations and deep cuts through the introduction of relatively small, closely spaced inclusions (usually steel bars) into a soil mass, the face of which is then locally stabilized. A zone of reinforced ground results that functions as a soil retention system.

Soil Nailing Applications

• Temporary and permanent excavation support/retaining walls
• Stabilization of tunnel portals
• Stabilization of slopes
• Repair of retaining walls

Soil Nails May Consist of;

• Reinforcing bars
• Steel tubing
• Steel angles

Types of Soil Nail

• Driven nail
• Grouted nail
• Jet grouted nail

Corrosion Protection

Corrosion protection is necessary for long-term temporary and/or permanent works.

• Epoxy Coatings
• Polyethylene Sheathing
• Cathodic Protection

Types of Facing

The type of facing depends on application and soil type. Current facings include:

• Shotcrete, generally reinforced with either
o Welded wire mesh
o Rebar
o Steel or polyester fibers
• Prefabricated concrete or steel panel
• Cathodic Protection

Suitable Application Media

Soil nailing is possible in a wide range of materials including:

• Clays
• Sandy soils
• Weathered rock; tallus slope deposits
• Heterogeneous and stratified soils

Soil nailing is not practical in:
• Soft, plastic clays
• Organics/Peat
• Loose (N 10), low density and/or saturated soils
• Fills (rubble, cinder, ash, etc.)

Geotechnical Parameters and Design Considerations for Soil Nailing

• Mechanical properties of soil
o Soil type(s) and density
o Moisture content
o Soil stratification
• Groundwater condition, seasonal changes and hydrology

Soil Nailing Drainage Systems

Drainage systems are incorporated into the nailed wall, reducing liquid pressure and preventing saturation of the reinforced ground. Drainage systems include:

• Geotextile facing
o Drilled in place relief wells
• Slotted plastic collection piping

Surface drainage control above and behind the retaining wall is also critical to the system.

Soil Nailing Design Steps

1.Perform geotechnical site investigation
2.Evaluate excavation/nailed wall geometry
3.Check wall stability - internal/external
4.Incorporate drainage control system with nail wall design
5.Finalize nailing layout and work sequence

Soil Nailing Quality Control

• Nailing installation sequence
o Verification testing - pull test to verify design strengths
o Progressive monitoring for design performance
• Conventional movement monitoring
o Inclinometers
o Optical survey of fixed targets
• Shotcrete
o Thickness
• Strength

Back to page