Correct form: Soil Retention by Nailing Method

Procedure for Soil Nailing (As per IS 14490:1997)

1. Site Investigation & Design

   • Conduct geotechnical investigation (IS 1892:1979) to determine soil properties.
   • Nail length: 0.7 to 1.0 times excavation height.
   • Nail spacing: Generally 1.0 m to 2.0 m horizontally & vertically.
   • Inclination: 10°–20° below horizontal.

2. Excavation

   • Excavation should be carried out in stages of 1.0–2.0 m depth.
   • Each stage should be stabilized with nails before moving further.

3. Drilling of Nail Holes

   • Diameter of hole: 100–200 mm (IS 14490 recommends 100–150 mm).
   • Holes drilled using rotary percussion rigs with compressed air or water flush.

4. Insertion of Reinforcement (Nails)

   • Nails generally consist of TMT bars (as per IS 1786) or steel tendons.
   • Centralizers to be used to maintain cover of ≥ 25 mm grout thickness.

5. Grouting

   • Grouting material: Cement slurry (IS 456 & IS 3370).
   • Water–cement ratio: 0.4–0.5.
   • Pressure grouting to ensure complete filling.

6. Shotcrete / Facing

   • Temporary or permanent facing provided by shotcrete (IS 9012:1978), wire mesh, or concrete panels.
   • Minimum thickness: 75 mm (temporary) to 150 mm (permanent).

7. Drainage

   • Weep holes or geosynthetics to relieve pore water pressure behind the nailed wall.

8. Testing of Nails

   • Proof load tests & verification tests must be conducted on selected nails (as per IS 14490).
   • Test load generally 1.25 to 1.5 times the design load.

9. Monitoring

   • Regular monitoring of wall deflection and soil movement during and after construction.

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✅ Key Reference IS Codes:

• IS 14490:1997 – Soil Nailing Guidelines
• IS 456:2000 – Plain & Reinforced Concrete Code
• IS 1786:2008 – High Strength Deformed Steel Bars
• IS 9012:1978 – Shotcreting Practice
• IS 3370 – Grouting Works