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Soil Nailing
Nanjundaswamy P.
Dept. of Civil Engineering
S J C E, Mysore
In-situ placement condition
In-situ driven condition
Soil Nailing
In-situ soil reinforcement technique
Reinforcing the ground by
passive inclusions
closely spaced
coherent gravity structure
Result – increase in overall shear strength
restraining displacements
Extension of New Austrian Tunneling Method
Steel reinforcing elements
Driven nails
Grouted nails
Jet-grouted nails
Corrosion-protected nails
Driven nails
Rods or Bars or metallic sections (Mild steel)
350 MPa
15 to 46 mm Ø
2 to 4 bars/sq.m
Homogeneous composite reinforced soil mass
Length max. 20m
Vibropercussion pneumatic or Hydraulic hammer
Rapid and economical (4 to 6 per hour)
Grouted nails
15 to 46 mm Ø
415Mpa
10 to 15 cm Ø bore holes
H and V spacing 1 to 3 m
Cement grouted by gravity or low pressure
Ribbed bars or special perforated tubes
Jet-grouted nails
30 to 40 cm thick
High pressure (> 20MPa) jet grouting
High frequency vibropercussion hammer
Provides recompaction and higher pull-out resistance
Corrosion-protected nails
Double protection schemes
Facing and structural retaing elements
Shotcrete
Welded wire mesh
Concrete and SteelCast-in-place panels
Prefabricated panels
Applications
Construction Sequence
AdvantagesElimination of footing
Elimination of backfilling behind wall
Reduction in quantities of reinforced concrete
Reduction in construction disturbance
Adaptability to different site conditions and soil profiles
Rapid and economical
Flexible mass – high degree of structural damping – suitable for seismically active regions
LimitationsEffective drainage systems
In plastic clayey soils – creep effect
Soft cohesive soils - Mobilisation of Pull-out capacity is not economical
Durability – metallic inclusions under aggressive environments
Soil – Nail Behavior
Typical Failure Modes
Typical Failure Modes
Typical Failure Modes
Failure Modes - Analysis
Failure Modes - Analysis
Failure Modes - Analysis
TUNNEL AT IISc
ROAD
ROAD
Conventional Retaining Wall
Design
Design of soil Nailed Retaining Structure
Based on charts• Gassler method• Davis method• …….
Gassler method
Stocker et al (1979) Known as German method
• Bilinear Sliding Surface (1981, 1996)
Gussler and Gudehus• Mohr-Coulomb criterion• Equilibrium – rigid soil wedge/failure
surface
Gassler method . . . .
Specific nailing density (µ)
� = �
�����
Normalised design load
�� = ���ℎ
� = γℎ� ������ ∅�
Gassler method . . . .
Gassler method . . . .
Gassler method . . . .
Gassler method . . . .
Gassler method . . . .
Gassler method . . . .