1. 1. presented by: Ankush Choudhury Under the guidance of Prof M.Deshmukh G.N.D.E.C BIDAR CIVIL ENGG. DEPT Soil Nailing
2. 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. 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. 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. 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. 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. 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. 8. Contd. Main components of a Soil Nail wall Grout is being placed with the help of pipes Typical PVC centralizer
9. 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. 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. 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
12. 12. MACHINERIES USED Drilling Equipments Grout Mixing Equipments Shotcreting/ Guniting Equipments Compressor
13. 13. Contd.. Typical drilling equipment Grout Mixing Instrument Shotcreting is done using a pipe
14. 14. Materials Used For Soil Nailing Steel Reinforcements Grout Mix Shotcrete/Gunite Grouted Reinforcements bars Grout Mix
15. 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. 16. Contd. Initial excavation lift and nail installation Typical drilling of soil nails with Rotary Method
17. 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. 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. 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. 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
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