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1. presented by: Ankush Choudhury Under the guidance of Prof
M.Deshmukh G.N.D.E.C BIDAR CIVIL ENGG. DEPT Soil Nailing
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. 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
13. Contd.. Typical drilling equipment Grout Mixing Instrument
Shotcreting is done using a pipe
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
16. Contd. Initial excavation lift and nail installation
Typical drilling of soil nails with Rotary Method
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