1. 4.4 SOIL NAILING
SOIL NAILING IS A REINFORCEMENT METHOD TO REINFORCE THE GROUND WITH STEEL BARS OR STEEL BARS IN GROUT FILLED HOLES. IT IS MAINLY USED IN EXCAVATIONS AND IN STABILISING SLOPES. IT IS A PRACTICAL AND PROVEN METHOD BUT DESIGN PRINCIPLES ARE STILL IN DISCUSSION.

2. NOTE THAT LOADS ARE NOT APPLIED DIRECTLY ON THE INCLUSIONS (I. E
NOTE THAT LOADS ARE NOT APPLIED DIRECTLY ON THE INCLUSIONS (I.E. MICROPILING)
INCLUSIONS PLACED IN THE SOIL TO MAINTAIN EQUILIBRIUM UNDER THE SOIL SELF-WEIGHT LOADING, AND SURCHARGE LOADING ON THE SOIL
IN SOIL NAILING THE REINFORCEMENT IS INSTALLED HORIZONTALLY OR NEAR HORIZONTAL TO IMPROVE THE SHEAR RESISTANCE OF SOIL BY ACTING MAINLY IN TENSION. NAILS ARE USUALLY ANGLED ACROSS THE POTENTIAL RUPTURE SURFACE

3. APPLICATION AREAS
A NEW CONSTRUCTION.
RETAINING WALLS
SLOPE STABILISATION
STABILISING TUNNEL PORTALS
B REMEDIAL WORK
REPAIR OF REINFORCED EARTH WALL
REPAIR OF MASONARY GRAVITY WALL
REPAIR OF ANCHORED WALLS
STABILIZATION OF FAILED SOIL SLOPES

4. 4.4.1 CONSTRUCTION STAGES
EXCAVATION IN LAYERS OF 1 M - 2 M DEPTH
COVERING THE EXPOSED SURFACE BY SHOTCRETE
NAILING WITH STELL BARS AND GROUTING
8-20 CM THICKNESS OF WALL FACE
20 MM - 28 MM DIAMETERS OF STEEL BARS (UPTO 50 MM)
NAIL /M2 NAILING DENSITY

5. EXCAVATION DEPTHS OF NEARILY VERTICAL CUTS SOIL TYPE
CUT DEPTH
(SANDY) Gravel
0.5 m (With capillary cohesion)
-1.5 m (cemented)
Sand
1.2 m (Medium Dense) with capillary cohesion
m (Dense & cap. cohesion)
-2.0 m (cemented)
Silt
1.2 m – 2 m
Clay
1.5 m (NC) – 2.5 m (OC)

6. 4.4.2 PROBLEM (UNSTABLE) CASES
ZONES OF (VERY) LOW DENSITY IN SANDS
DRY SANDS (W/C LESS THAN 1%)
EXTERNAL VIBRATIONS
INCLUSIONS OR LARGER STONES OR ROCK PIECES
SEEPAGE PRESSURE OF WATER LAYERS
DRIVING & PERCUSSING OF STEEL REINFORCEMENT (THE SYSTEM HURPINOISE)
SYSTEM BAUER
PREDRILLING BOREHOLES WITHOUT CASING
PREDRILLING BOREHOLES WITH CASING
SPECIAL (JET BOLTING SYSTEM, E.G. HIGH INJECTION PRESSURES)

9. 4.4.3 .DRAINAGE AND FACING STABILITY REGARDING EXTERNAL FORCES
THE REINFORCED ZONE MUST BE ABLE TO RESIST THE OUTWARD THRUST FROM THE UNREINFORCED INTERIOR, WITHOUT SLIDING
THE COMBINED LOADING FROM THE REINFORCED ZONE SELF WEIGHT AND THE LATERAL SOIL THRUST IT IS RESISTINNG MUST NOT CAUSE A FOUNDATION BEARING FAILURE.
STABILITY OF NAILED STRUCTURE MUST BE CHECKED AGAINST THE DEEPER SEATED FAILURE MECHANISMS.

10. INTERNAL STABILITY
THE REINFORCING ELEMENTS MUST BE INSTALLED IN A PATTERN DENSE ENOUGH TO ENSURE AN EFFECTIVE INTERACTION WITH THE SOIL IN THE REINFORCED ZONE.
THE REINFORCEMENT ELEMENTS MUST ALSO HAVE SUFFICIENT LENGTH & CAPACITY TO ENSURE A STABLE REINFORCED ZONE.
EACH INDIVIDUAL REINFORCEMENT SHOULD BE CAPABLE OF HOLDING THE SOIL IMMEDIATELY SURROUNDING IT IN EQUILIBRIUM, (I.E. CONTROLS SPACING)
- OVERALL SLIP FAILURE IN THE REINFORCED ZONE MUST ALSO BE CONSIDERED TO AVOID FAILURE BY INSUFFICIENT BOND OR BREAKING OF REINFORCEMENT (CONTROLS LENGTH)