U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
| REPORT |
| This report is an archived publication and may contain dated technical, contact, and link information |
 |
| Publication Number: FHWA-HRT-14-094 Date: February 2015 |
Publication Number: FHWA-HRT-14-094 Date: February 2015 |
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Geosynthetic reinforced soil (GRS) for load-bearing applications has been identified by the Federal Highway Administration (FHWA) as a proven, market-ready technology and is being actively promoted through the agency's Every Day Counts initiative. With the publication of the FHWA interim design guidance for GRS abutments and integrated bridge systems, presented in GRS Integrated Bridge System (IBS) Interim Implementation Guide (FHWA-HRT-11-026), FHWA took the first steps to differentiate the design of GRS and conventional, larger-spaced geosynthetic mechanically stabilized earth (GMSE). This was based on considerable research and the change in behavior observed when reinforcement is closely spaced (i.e., less than about 12 inches (30.48 cm)). Because of its similarities to GMSE walls, however, there are some misconceptions about the design and behavior of closely spaced GRS systems. This synthesis report outlines the background and research for some of the most pertinent changes related to the design differences between GRS and GMSE: embedment length, reinforcement pullout, eccentricity, lateral earth pressures and connection strength, the W equation for required reinforcement strength, and long-term reduction factors for geosynthetic materials. This report can be used by transportation agencies to support design changes related to closely spaced GRS systems.
Jorge E. Pagán-Ortiz
Director, Office of Infrastructure
Research and Development
Notice
This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.
The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.
Quality Assurance Statement
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Technical Report Documentation Page
| 1. Report No.
FHWA-HRT-14-094 |
2. Government Accession No. | 3 Recipient's Catalog No. | ||
| 4. Title and Subtitle
Synthesis of Geosynthetic Reinforced Soil Design Topics |
5. Report Date February 2015 |
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6. Performing Organization Code HRDI-40 |
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| 7. Author(s)
Jonathan T.H. Wu and Phillip S.K. Ooi |
8. Performing Organization Report No.
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9. Performing Organization Name and Address Department of Civil and Environmental Engineering, University of Hawaii at Manoa, 2540 Dole Street, Honolulu, HI 96822 Civil Engineering Department, University of Colorado-Denver, Denver, CO 80217 |
10. Work Unit No. (TRAIS) |
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11. Contract or Grant No. N/A |
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| 12. Sponsoring Agency Name and Address
Office of Infrastructure R&D |
13. Type of Report and Period Covered
Technical |
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14. Sponsoring Agency Code
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15. Supplementary Notes The FHWA Contracting Officer's Technical Representative was Mike Adams, HRDI-40. FHWA technical reviewers were Jennifer Nicks, Daniel Alzamora, and Khalid Mohamed. |
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| 16. Abstract
This report synthesizes six topics related to geosynthetic reinforced soil (GRS) design: embedment length, pullout check, eccentricity, lateral pressures, the W-equation for GRS capacity and required reinforcement strength, and geosynthetic reduction factors. The synopsis for each topic includes a summary of the relevant research and a review of pertinent issues. The intent is not to provide recommendations but to explain the methodology behind the Federal Highway Administration's (FHWA) composite design for GRS, which is different than that for geosynthetic mechanically stabilized earth. The synopses support the FHWA's GRS Integrated Bridge System (IBS) Interim Implementation Guide, (FHWA-HRT-11-026). |
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| 17. Key Words
Geosynthetic reinforced soil, pullout, embedment length, eccentricity, overturning, connection strength, required reinforcement strength, abutment, integrated bridge system, geotextile |
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161. http://www.ntis.gov |
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19. Security Classification Unclassified |
20. Security Classification Unclassified |
21. No. of Pages 86 |
22. Price | |
| Form DOT F 1700.7 | Reproduction of completed page authorized |
SI* (Modern Metric) Conversion Factors
Figure 1. Drawing. Pullout failure, exaggerated for purposes of illustration
Figure 2. Illustration. Effects of facing connection condition on tensile force distribution in reinforcement
Figure 3. Illustration. Sequence of cutting of the PWRI test wall
Figure 4. Chart. The resulting horizontal movement of the PWRI test wall.
Figure 5. Chart. Lateral stress/pressure on different sections of a GRS wall.
Figure 6. Drawing. Free body diagram, cantilever wall system for overturning calculations
Figure 7. Equation. Estimated maximum bearing pressure, σ subscript max
Figure 8. Equation. Estimated minimum bearing pressure,σ subscript min
Figure 9. Equation. Simplified estimated maximum bearing pressure,σ subscript max.
Figure 10. Equation. Simplified estimated minimum bearing pressure,σ subscript min
Figure 11. Equation. Resultant force from the toe,γ subscript R
Figure 12. Drawing. Bearing pressure diagram-resultant force within middle third.
Figure 13. Drawing. Bearing pressure diagram-resultant force on middle third.
Figure 14. Drawing. Bearing pressure diagram-resultant force outside middle third
Figure 15. Equation. Resultant ratio, RR.
Figure 16. Equation. Percent area of footing in compression, A subscript fc (in percent)
Figure 17. Drawing. Forces on a rectangular rigid wall
Figure 18. Equation. Vertical component of resultant force at offset e, Rve
Figure 19. Equation. Force e.
Figure 20. Equation. Safety factor, F
Figure 21. Equation. Footing width, B
Figure 22. Equation. Value of footing width B for liftoff to occur.
Figure 23. Photo. First negative batter GRS wall constructed in Colorado for CDOT.
Figure 24. Photo. GRS wall in New Zealand with a negative.
Figure 25. Photo. Research on negative batter GRS walls in Japan
Figure 26. Chart. Residual lateral stress induced by vibratory plate compaction.
Figure 27. Chart. Vertical stress distribution at 6-kN (1.35-kips) vertical load on the GRS(a) without and (b) with reinforcement
Figure 28. Chart. Horizontal stress distribution at 6-kN (1.35-kips) vertical load on the GRS (a) without and (b) with reinforcement
Figure 29. Chart. Shear stress distribution at 6-kN (1.35-kips) vertical load on the GRS (a) without and (b) with reinforcement
Figure 30. Drawing. Founders/Meadows bridge abutment cross-section and instrumentation
Figure 31. Drawing. GRS mini-pier elevation plan.
Figure 32. Drawing. GRS mini-pier elevation plan.
Figure 33. Chart. Measured increase in lateral pressures on the facing of GRS mini-piers during load test in kPa
Figure 34. Charts. Measured increase in lateral pressures on the facing of GRS mini-piers during load test in kN/m2
Figure 35. Diagram. Bin pressure diagram
Figure 36. Equation. Total lateral thrust, F subscript bin, as a function of the spacing between reinforcements, S subscript v, and peak bin pressure σ subscript h.
Figure 37. Equation. Total lateral thrust, F subscript bin, in terms of the coefficient of active earth pressure.
Figure 38. Drawing. GMSE wall configuration showing nonreinforced backfill zones
Figure 39. Drawing. Lateral earth pressure distribution against wall facing exerted by the nonreinforced backfill
Figure 40. Equation. Connection force F.
Figure 41. Photo. Grand County, Colorado, wall with a maximum height of 55 ft (16.8 m).
Figure 42. Equation. Increase in lateral pressure Δ σ subscript h.
Figure 43. Drawing. Definition of angles α and δ.
Figure 44. Chart. Increase in lateral stress due to 4,000-psf (191.5-kPa) vertical stress on a 4-ft- (1.2-m-) wide footing with a 1-ft (.3-m) setback.
Figure 45. Drawing. Mohr circles for unreinforced and reinforced soil
Figure 46. Equation. Major principal stress σ subscript 1
Figure 47. Equation. Confining stress due presence of reinforcement σ subscript 3R
Figure 48. Equation. Capacity of the GRS σ subscript 1R
Figure 49. Equation. Additional confining stress as function of reinforcement tensile strength divided by the reinforcement spacing Δ σ subscript 3.
Figure 50. Equation. Modified version of the equation in figure 49 for additional confining stress, Δ σ subscript 3 imposed with the W factor.
Figure 51. Equation. W factor
Figure 52. Equation. Capacity of the GRS,σ subscript 1R.
Figure 53. Equation. Expansion of the equation in figure 52 for the capacity of the GRS, σ subscript 1R, to include cohesion.
Figure 54. Graph. Predicted versus measured capacity of large-scale GRS tests using the equation in figure 52.
Figure 55. Graph. Predicted versus measured capacity of large-scale GRS tests using the equation in figure 52 without the W term.
Figure 56. Equation. Allowable reinforcement design strength, T subscript a.
Figure 57. Illustration. Schematic diagram of a SGIP test
Table 1. Research: walls and abutments with uniform "short" reinforcement lengths.
Table 2. Research: walls and abutments with "truncated base" reinforcement lengths.
Table 3. Resultant force location and impact on safety against overturning, base area in compression, and bearing pressure diagram.
Table 4. Key points relating to the need to limit the eccentricity in the design of GRS walls.
Table 5. Comparison of Wu's versus Soong and Koerner's calculated lateral thrusts as a function of reinforcement spacing.
Table 6. Predicted versus measured lateral pressures on reinforced soil wall facing.
Table 7. Prediction data for large-scale tests.
| AASHTO | American Association of State Highway and Transportation Officials |
| ASD | Allowable Stress Design |
| CDOT | Colorado Department of Transportation |
| CIS | Compaction Induced Stresses |
| CMU | Concrete Masonry Unit |
| DACSAR | Deformation Analysis Considering Stress Anisotropy and Reorientation |
| FEM | Finite Element Model |
| FHWA | Federal Highway Administration |
| GMSE | Geosynthetic Mechanically Stabilized Earth |
| GRS | Geosynthetic Reinforced Soil |
| IBS | Integrated Bridge System |
| LRFD | Load and Resistance Factor Design |
| MARV | Minimum Average Roll Value |
| MSE | Mechanically Stabilized Earth |
| NCHRP | National Cooperative Highway Research Program |
| NCMA | National Concrete Masonry Association |
| NGI | Norwegian Geotechnical Institute |
| NHI | National Highway Institute |
| PWRI | Public Works Research Institute (Japan) |
| RRR | Reinforced Railroad/Road with Rigid facing |
| SGIP | Soil-Geosynthetic Interactive Performance |
| USACE | U.S. Army Corps of Engineers |
