1. بسم الله الرحمن الرحيم Soil Nailing for slope stability
4/28/2017
King Fahd University of Petroleum & Minerals
Civil Engineering Department
Term (101), CE553
Soil and site improvement
Soil Nailing for slope stability
Instructor : Dr. Talat Bader
Presented by: Salem Babtain
ID No
CE 553
CE 553
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2. Outline Introduction Literature review Slope Failure Soil Nailing
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Outline
Introduction
Literature review
Slope Failure
Soil Nailing
Case Studies
Conclusion
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3. Soil nailing is used mainly to protect soil slope failure
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Introduction
Soil nailing is a technique in which soil slopes, excavations or retaining walls are reinforced by the insertion of relatively slender elements - normally steel reinforcing bars.
Soil nailing is used mainly to protect soil slope failure
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4. Literature Review 1960's and earlier in 1961 in the 1970's in 1972
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Literature Review
"New Austrian Tunneling Method" (NATM), in which grouted rock bolts and shotcrete were used for supporting tunnels
1960's and earlier
in 1961
permanent support of retaining walls in a cut in soft rock in France.
The use of grouted "soil nails" and driven soil nails, which consist of solid steel bars and steel angle iron, continued to grow in the 1970's, in France, Germany and north America
in the 1970's
The first wall built in France using current soil nail techniques was reported to have been built by Soletanche, in Versailles
in 1972
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5. Guidelines and Manuals
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Guidelines and Manuals
One of the first national guideline publications for soil nailing. ( In Japan)
In 1987
in France (Clouterre Program)
$ 5 million study to develop design methodology for soil nail walls
"Recommendations of Clouterre," published in 1991
In the 1991
Federal Highway Administration published its "Manual for Design and Construction of Soil Nail Walls.“
In 1993 (FHA)
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6. Slope Failure What is slope failure ?
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Slope Failure
What is slope failure ?
-The slope can not support itself
- Gravitational and seepage forces cause disturbing force
- Soil friction provide resisting force
- If disturbing moment > resisting moment Slope will failure
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7. 4/28/2017
Type of slope failure
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8. 4/28/2017
Type of landslide
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9. Slope Failure Major landslide in past history 18 person killed
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Slope Failure
Major landslide in past history
18 person killed
67 person killed
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10. Factors affecting slope failure
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Factors affecting slope failure
Major landslide in past history
Geometrical changes
Shocks & vibrations
Change in water regime
Removal of vegetation
Weathering
18 person killed
67 person killed
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11. Slope stabilization methods
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Slope stabilization methods
Natural
Masonry
Soil Nailing
Others
Shotcrete
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12. Soil nailing method Main function of soil nailing is:
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Soil nailing method
Main function of soil nailing is:
Provide a resisting force against slope failure
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13. Soil uses Soil nailing is used to reinforce -tunnels wall support
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Soil uses
Soil nailing is used to reinforce
-tunnels wall support
-soil cut slopes
-retaining wall support
-excavations,
-disturbed terrain and
-natural hillsides stabilize
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14. Principle of Soil nailing
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Principle of Soil nailing
Active Zone
Slip Surface
Passive Zone
- In slope stability calculations, the result needs to obviously ensure that the resisting forces are greater than the force tending to cause slope failure.
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15. There are three types of FOS
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Factor of Safety ( FOS )
- FOS is defined as the ratio of total resisting forces to total disturbing forces or total overturning moment. 1-
There are three types of FOS 2- 3-
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16. 4/28/2017
Nails
Generally small-diameter nails (15-46 mm) Driven nails are the quickest and most economical to install.
Driven Nail
Steel bars, with diameters ranging from 15 to 46 mm, stronger than driven nails Grouted nails are inserted into boreholes of cm and then cement-grouted.
Grouted Nail
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17. 4/28/2017
Nails
Launched nails
Nails are fired directly into the soil with a compressed-air launcher. Used primarily for slope stabilization, this technique involves the least site disturbance.
Jet-grouted nails
A composite of grouted soil and a central steel rod, up to 40 cm thick. Nails are installed using a high-frequency vibropercussion hammer, and cement grouting is injected during installation.
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18. Equipments used Drilling Equipments CE 553 4/28/2017
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19. Equipments used Grout Mixing Equipment mortar grouting pump CE 553
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Equipments used
Grout Mixing Equipment
mortar grouting pump
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20. Equipments used Shotcreting Equipment The compressor shall have
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Equipments used
Shotcreting Equipment
The compressor shall have
Very high rate capacity.
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21. Components of soil nail
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Components of soil nail
Nails
Centralizer
Grout
Head
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22. Construction Sequence
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Construction Sequence
1-Initial Excavation
2-Drilling of holes
3-Insertion of nail
4-Grouting
5-Head construction
6-Shotcrete
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23. Construction Sequence
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Construction Sequence
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24. Advantages Economic Construction redundancy
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Advantages
Economic
Relatively Low Cost. According to Cornforth (2005) mentioned that, soil nailing can result in a cost saving of 10 to 30 percent when compared to tieback walls.
Construction techniques are simple and quick. So, rate of construction fast.
Construction
redundancy
If any one of soil nails becomes overstressed, it will not cause failure of the slope. It will redistribute the overstress to the adjoining nails system Ortigao (2004).
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25. Advantages Adaptability Flexibility
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Advantages
Soil nails can be used in heterogeneous ground. Soil nailing generally is more feasible than other techniques. This is because it involves only small-diameter drilling for the installation of the inclusions
Adaptability
Flexibility
Soil nailing retaining structures is more flexible than other slope sterilization technique. It can be integrated with other earth retaining system such as Tie-back wall and retaining wall.
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26. Advantages Adaptability Flexibility
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Advantages
Soil nails can be used in heterogeneous ground. Soil nailing generally is more feasible than other techniques. This is because it involves only small-diameter drilling for the installation of the inclusions
Adaptability
Flexibility
Soil nailing retaining structures is more flexible than other slope sterilization technique. It can be integrated with other earth retaining system such as Tie-back wall and retaining wall.
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27. Limitations Unsuitable soil Groundwater
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Limitations
Unsuitable soil
Cohesionless soil slopes are not suitable for soil nails slope stability. This is because during the drilling of the hole or un-grouted hole may collapse
Groundwater
Soil nailing is not suitable above groundwater level. a drilled hole cannot support itself due to water saturation and the hole will collapse. Furthermore, water cement ratio in grouting will effect.
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28. Limitations Vibration sensitive prolong downpours Utilities
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Limitations
Vibration sensitive
drilling may affect the adjacent structures. Some building structures are vibration sensitive such as Historical Buildings.
prolong downpours
Slope failures can be seen Sometimes especially during raining seasons or after heavy prolong downpours. Ground becomes fully saturation, in this case soil nailing combined with retaining wall is better.
Utilities
sometimes utilities such as buried water pipes, underground cables and drainage systems cause a problem facing soil nails inside the slope.
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29. Soil nailing failure Pullout failure
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Soil nailing failure
Pullout failure
Result of insufficient embedded length into the resistant zone
Resistant zone
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30. Soil nailing failure Nail tendon failure
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Soil nailing failure
Nail tendon failure
Results from inadequate tensile strength of the nails to provide the resistant force to stabilize the slope
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31. Soil nailing failure Face failure
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Soil nailing failure
Face failure
Results if relatively small and nominal shotcrete thickness and reinforcement is adequate.
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32. Site Investigation Site Investigation -Desk study -Site Reconnaissance
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Site Investigation
Site Investigation
-Desk study
-Site Reconnaissance
-Collection of field data including
Investigation and laboratory testing.
-Follow-up investigation and design review
during construction
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33. -Collapse of drilled-hole
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Major impacts
The major impacts to soil nailing works
-Loss of grout though the fractured rock
mass, open joints and cavities
-Collapse of drilled-hole
-Poor nail-to-soil interface resistance due
to disturbance of drilled-hole
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34. 4/28/2017
Case Study (1)
Cowboy Stadium
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35. Case Study (1) DYWIDAG Company -Cowboy stadium construction CE 553
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Case Study (1)
Vertical Slope 18 m below the ground
They used:
nails
About 670 tone
16m to 18m bars long
DYWIDAG Company
-Cowboy stadium construction
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36. Case Study (1) Advantage of soil nailing wall Fast work
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Case Study (1)
Advantage of soil nailing wall
Fast work
flexibility of soil nail construction with progress of excavation.
cost relatively cheaper than other method.
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37. Case Study (2) Slope failure
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Case Study (2)
Slope failure
Slope failures not only will cause economic loss to the public but also may result in loss of life
Malaysia, 1999
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38. Just view days after soil nails constructed, slope failed
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Case Study (2)
Cause of failure
-Prolong rain fall
-Design mistakes
-failure was behind
the soil nails
Just view days after soil nails constructed, slope failed
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39. Remedial Implementation
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Case Study (2)
Remedial Implementation
In this case the proper solution was:
Build a retaining wall combined with soil nailing.
Gentle slope behind the retaining wall
Drainage system should be used
Reinforced soil nails wall was selected in this case after comparison of construction cost and time with other types of retaining walls
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40. 4/28/2017
Case Study (2)
3 years after the completion of the remedial works
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41. 4/28/2017
Conclusion
Soil nail construction has been shown to be a simple technology and does not need complex machines.
This method can provide a lower construction, period, and can provide good stabilize for slope failure.
Soil nailing has some advantages and some limitation. So, proper investigation and design should be taken.
soil nailing should be avoided in some cases
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42. Thank you
Q & A
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