2. CONTENTS
1. INTRODUCTION
2. ORIGIN AND DEVELOPMENT
3. FAVOURABLE UNDER-GROUND CONDITIONS
4. TYPES OF GROUNDS SUITABLE FOR SOIL NAILING
5. COMPONENTS OF A SOIL NAIL WALL
6. TYPES OF NAILS USED
7. DESIGN REQUIREMENTS
8. MACHINERIES USED
9. MATERIALS USED
10. CONSTRUCTION SEQUENCES
11. APPLICATIONS
12. ADVANTAGES
13. CONCLUSION
14. REFERENCES
3. INTRODUCTION
Soil nailing is a technique used to reinforce and
strengthen existing ground.
Soil nailing consists of installing closely spaced bars into
a slope or excavation as construction proceeds from top
down.
It is an effective and economical method of constructing
retaining wall for excavation support, support of hill cuts,
bridge abutments and high ways.
4. ORIGIN AND DEVELOPEMENT
It evolved from the New Austrian Tunneling method which is a system for
underground excavations in rock in 1960
The first application of soil nailing was implemented in 1972 for a railroad
widening project near Versailles, France. A 18m (59ft) high wall was to be
soil nailed
Germany and USA first used soil nailing in 1975 and 1976 respectively
In India use of soil nailing technology is gradually increasing and
guidelines have been made by IRC with the help of Indian Institute of
Science, Bangalore.
5. FAVOURABLE UNDER-GROUND
CONDITIONS
• The excavated soil should be able to stand unsupported in 1m-2m
high vertical cut for maximum 2 days
• Soil nails should be located above the ground –water table
• The ground conditions should allow drill holes to be advanced
without using drill casings
6. TYPES OF GROUND SUITABLE FOR SOIL
NAILING
• Stiff to Hard Fine-Grained Soils: Includes hard clays, silt clays and
sandy silts. Have SPT value(N) around 9blows/300mm. Fine-grained
soils possess low plasticity i.e. P.I. <15
• Dense to Very Dense Granular Soils: Includes sand and gravel with
SPT values > 30 and fines about 10 to 15 percent
• Weathered rock with no Weakness Planes: May provide a suitable
supporting materials for soil nails until there are no weakness planes i.e.
planes dipping into the excavation
• Glacial Soils: Glacial outwash materials are suitable for soil nailing as
they are dense, well graded materials
7. COMPONENTS OF A SOIL NAIL WALL
• Nail Bars: Steel reinforcing bars of nominal tensile strength of 420
Mpa (Grade 60) and 520 Mpa (Grade 75) are used.
• Nail Head: Two main parts: A) bearing plate, hex nut and washers;
B) the headed-stud.
• Grout: A neat cement grout is used. Sand-cement grout can also be
used. Water/cement ratio for grout ranges from 0.4 to 0.5
• Centralizers: Made of polyvinyl chloride (PVC).It ensures that a
minimum thickness of grout completely covers the nail bar.
8. Contd….
Main components of a Soil Nail
wall
Grout is being placed with
the help of
pipes
Typical PVC centralizer
9. TYPES OF NAILS USED
Drilled and Grouted Soil Nail: Approximately 100-200mm in diameter.
Spaced at about 1.5m apart.
Driven Soil Nails: Relatively small in diameter about 19 to
25mm.Spaced at approx 1 to 1.2m apart. Mechanically driven. Allows
faster installation
Self Drilling Soil Nails: Consist of hollow bars which can be drilled and
grouted in one operation. Allows faster installation than drilled grouted
nails and provides corrosion protection
Jet-Grouted Soil Nails: First step, allows advancement of the nail to the
final location. In second step, the bars are installed using vibro-
percussion drilling methods
Launched Soil Nails: Bare bars are launched into the soil using a firing
10. DESIGN REQUIREMENTS
After a preliminary analysis
of the site, initial designs of
the soil nail wall can be
begin.
This begins with a selection
of limit states and design
approaches.
The two most common limit
states used in soil nail wall
design is strength limit and
service limit states.
11. LIMIT STATES
The strength limit state is the
limit state that addresses
potential failure mechanisms or
collapse states of the soil nail
wall system.
The service limit state is the
limit state that addresses loss
of service function resulting
from excessive wall
deformation and is defined by
restrictions in stress,
deformation and facing crack
width under regular service
Modes of failure
14. Materials Used For Soil Nailing
Steel Reinforcements
Grout Mix
Shotcrete/Gunite
Grouted Reinforcements
bars
Grout Mix
15. CONSTRUCTION SEQUENCES
1. Excavation
2. Drilling nail
holes
3. Installation
and grouting
nails
4. Construction
of temporary
shotcrete
facing
5. Construction
of subsequent
levels; and
17. APPLICATIONS
Stabilization of railroad and highway cut slopes
Excavating retaining structures in urban areas for high-rise building
and underground facilities
Tunnel portals in steep and unstable stratified slopes
Construction and retrofitting of bridge abutments
Stabilizing steep cuttings
Stabilizing of existing over-steep embankments
Providing long term stability to existing concrete structures without
demolition and rebuild costs
18. ADVANTAGES
CONSTRUCTION:
Requires smaller space as they are shorter
Less disruptive to traffic
Rapid and uses less construction materials
Advantageous at sites with remote access
PERFORMANCE:
Relatively flexible
Total deflections are within tolerable limits
Performed well during seismic events
COST:
Economical
Shotcrete facing is less costly
19. CONCLUSION
Soil nailing is an accepted technology, the theoretical aspects of
which are well understood and well reported in technical literature.
However, research indicates that there are few practical guidelines
available that offer a comprehensive, experience-based insight into
the construction considerations that should be addressed before a
soil nail system design is finalized and implemented.
20. REFERENCES
http://www.deepexcavation.com/en/soil-nail-wall
http://www.moretrench.com/b_literature_article.php
http://en.wikipedia.org/wiki/Soil_nailing
Manual for Design and Construction Monitoring of Soil Nail
walls, US Department of Transportation, Federal Highway
Administration.
Guide to Soil Nail Design and Construction, Geotechnical
Engg Office, Civil Engineering and Development Department,
The Government of the Hong Kong.
http://www.google.com
