![Page 1: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/1.jpg)
Geotextiles in Coastal RevetmentsGeotechnical Considerations Lex NielsenSeptember 2009
![Page 2: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/2.jpg)
Section HeaderSub-heading
Stockton Surf Club sandbag revetment
Stockton Beach rock revetment
STORM 9TH March 2001
![Page 3: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/3.jpg)
Stockton Surf Club Sandbag Seawall
Soil Filters
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 4: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/4.jpg)
Stockton Seawall- PWD Design
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 5: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/5.jpg)
Soil Mechanics 101
Slope Stability
Sand @ 28°
Rock @ 35°
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 6: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/6.jpg)
Soil Mechanics 101Internal Friction (Φ)
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 7: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/7.jpg)
Soil Mechanics 101Shear strength
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 8: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/8.jpg)
Soil Mechanics 101Typical shear strengths / stable infinite slopes
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 9: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/9.jpg)
Revetment Structure
• Armour layer
– Rock, Concrete units, sandbags
• Underlayer
– Rock
– Sandbag
• Separation layer– Rock filters– Geotextile
• Base layer– Rock core– Dune sand– Soil embankment
The slope stability of each layer’s interface needs to be examined in respect of inter-facial frictional strength
The revetment structures comprise several layers
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 10: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/10.jpg)
Geotextile Interface Frictional PropertiesSand/GTX (Φsg)
GTX/GTX (Φgg)
1. Manufacturers Recommendations2. Soil Filters testing (Terrafax 1200R)3. Literature review
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 11: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/11.jpg)
Sand/GTX (Φsg) Manufacturers Recommendations
Exxon:
tan Φsg = CI × tanΦs
CI = 0.7 – 0.8
tan Φsg = 0.7 to 0.8 × tanΦs
For Φs = 32° – 35°
Φsg = 24° – 29°
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 12: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/12.jpg)
Sand/GTX (Φsg)Geofabrics-Elco
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 13: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/13.jpg)
Geofabrics-ElcoSand/Terrafix 1200R
Φsg = 31°
![Page 14: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/14.jpg)
Sand/GTX (Φsg)Literature review1. Dixon, N., DRV Jones & GJ Fowmes (2006). “Interface shear strength variability
and its use in reliability-based landfill stability analysis”, Geosynthetics International, vol. 13, no. 1, pp 1-14.
2. Koerner, GR & D Narejo (2005). Direct Shear Database of Geosynthetic-to-Geosynthetic and Geosynthetic-to-Soil Interfaces, Geosynthetic Research Institute, GRI Report No. 30, June.
3. Martin JP, RM Koerner & JE Whitty (1984). “Experimental friction Evaluation of Slippage between Geomembranes, Geotextiles and Soils”, Proc. Int. Conf. Geomembranes, Denver, USA pp 191-196.
4. Williams, ND & MF Houlihan (1987). “Evaluation of Interface Friction Properties between Geosynthetics and Soils”, Proc. of Geosynthetics ’87 Conference, New Orleans, USA, February, pp 616-627.
5. Tan, SA, SH Chew & WK Wong (1998). “Sand-geotextile interface shear strength
by torsional ring shear tests”, Geotextiles and Geomembranes 16 pp161-174.
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 15: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/15.jpg)
Sand/NWNPGTX Friction AngleDixon, Jones & Fowmes (2006)
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 16: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/16.jpg)
Sand/NWNPGTX Friction AngleDixon, Jones & Fowmes (2006)
For low confining stress data (10kPa-30kPa), adopting a characteristic value being the mean minus 1.0 SD, ensuring about 90% of the data lie above the value, results in (for σn=10kPa):
sg = 27
= 34.5
Low Confining Stress Data
= 27.1
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 17: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/17.jpg)
Sand/NWNPGTX Friction Angle Koerner, GR & D Narejo (2005)
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 18: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/18.jpg)
Sand/NWNPGTX Friction Angle Martin Koerner & Whitty (1984)
Present two test results:
• 30 for Ottawa sand
• 26 for concrete sand
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 19: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/19.jpg)
Sand/NWNPGTX Friction Angle Williams & Houlihan (1987)
Advocate the use of a large shear box (305 mm 305 mm).
The CI was around 0.9 for needle-punched geotextile with clean sands.
For Φs = 32° – 35°
Φsg = 29° – 32°
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 20: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/20.jpg)
Sand/NWNPGTX Friction Angle Tan, SA, SH Chew & WK Wong (1998)
Peak = 33°
Residual = 26°
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 21: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/21.jpg)
Summary ΦsgSource Typical Result
Manufacturer Exxon 24° – 29°
Geofabrics Elco 31°
Dixon, Jones & Fowmes 27°
Koerner & Narejo 23°
Martin Koerner & Whitty 26° – 30°
Williams & Houlihan 29° – 32°
Tan, Chew & Wong 26°
Average 27.5
1/ tan 27.5° = 1.9; 1.5/tan 27.5° = 2.9
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 22: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/22.jpg)
NWNPGTX/NWNPGTX Friction Angle Geofabrics-Elco
Peak: 1.0/tan26° = 2.0 1.5/tan26° = 3.1Residual: 1.0/tan20° = 2.7 1.5/tan20° = 4.1
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 23: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/23.jpg)
NWNPGTX/NWNPGTX Friction Angle
From Coghlan, Carley, Cox Blacka, Mariani, Restall, Hornsey & Sheldrick, Coasts & Ports 2009
![Page 24: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/24.jpg)
NWNPGTX/NWNPGTX Friction Angle
From Coghlan, Carley, Cox, Blacka, Mariani, Restall, Hornsey & Sheldrick, Coasts & Ports 2009
![Page 25: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/25.jpg)
Section HeaderSub-heading
Sandbag/Geotextile Friction?Sandbag/Geotextile Friction?
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 26: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/26.jpg)
35°
30°20°
1 : 1.5
1 : 2
1 : 3
terrafix vs Sand
Woven vs Sand
Standard Slope
terrafix vs Sand
Woven vs Sand
Standard Slope
terrafix vs Sand
Woven vs Sand
Standard Slope
Typical Angles
High Elongation Geotextile Relies on interlock
Low Elongation Geotextile Relies on stacking
Infinite slopes - For Factor of Safety = 1.0
i.e. slope = 1/tanΦ
For sand, Φ = 33°1/tanΦ = 1.5
NWNPGTX on NWNPGTX
27°
33°
NWNPGTX on sand
Sand slope
1:2.7
1:2.0
1:1.5
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 27: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/27.jpg)
Coastal RevetmentsCoastal revetments will have factors of safety higher than those for infinite slopes because of:• Finite height• Toe
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 28: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/28.jpg)
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 29: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/29.jpg)
On an Infinite 2:1 slope for Φsg = 29°, FoS = 2 × tan29° = 1.1Rock toe improves FoS from 1.1 to 1.5 Toe is critical for stability
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 30: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/30.jpg)
Small Rock Revetment on Sand 4m High with toeSensitivity of FoS to Slope and adopted Φsg
Slope 1:2.5
Slope 1:2.0
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 31: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/31.jpg)
Small Rock Revetment on Sand 4.0m High with toeAlternate (preferred) design
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 32: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/32.jpg)
ConclusionsFor preliminary text-book design of revetments using non-woven needle-punched geotextiles, recommend adopting:
Φsg = 27°Φgg = 20°
For the use of geotextile underneath a rock armoured revetment, GTX/sand interface slope must be flatter than 1:2.5 for an adequate factor of safety for overall geotechnical stability
For overall geotechnical stability of sandbag armoured revetment slopes in sand, slopes must be flatter than 1:3.0
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 33: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/33.jpg)
Section HeaderSub-heading
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 34: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/34.jpg)
Section HeaderSub-heading
IEAust Maritime Panel - Geotextiles in Coastal Revetments
![Page 35: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/35.jpg)
Section HeaderSub-heading
![Page 36: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/36.jpg)
Page heading• This is the first bullet point
(Font - Arial 20)– Sub-text of the bullet above
(Font - Arial 18)
• Second bullet– Sub-text of the bullet above.
Sometimes this text may fall onto two lines or more.
• Third bullet– Sub-text of the bullet above.
Sometimes this text may fall onto two lines or more.
Sub-heading
• This is the first bullet point (Font - Arial 20)– Sub-text of the bullet above
(Font - Arial 18)
• Second bullet– Sub-text of the bullet above.
Sometimes this text may fall onto two lines or more.
• Third bullet– Sub-text of the bullet above.
Sometimes this text may fall onto two lines or more.
![Page 37: Geotextiles in Coastal Revetments Geotechnical Considerations Lex Nielsen September 2009](https://reader036.vdocuments.site/reader036/viewer/2022062321/568139c4550346895da16a6f/html5/thumbnails/37.jpg)
Section HeaderSub-heading