Geosynthetic Design & Construction Guidelines NHI Course No. 132013-Reference-Manual-Final-August-2008

8/20/2019 Geosynthetic Design & Construction Guidelines NHI Course No. 132013-Reference-Manual-Final-August-2008

http:///reader/full/geosynthetic-design-construction-guidelines-nhi-course-no-132013-reference-manual-final-augu… 1/611

U.S. Department of Transportation Publication No. FHWA NHI-07-092

Federal Highway Administration August 2008

NHI Course No. 132013____________________________

Geosynthetic Design & Construction GuidelinesReference Manual

National Highway Institute



NOTICE

The contents of this report reflect the views of the authors, who are responsible for the

facts and the accuracy of the data presented herein. The contents do not necessarily

reflect policy of the Department of Transportation. This report does not constitute a

standard, specification, or regulation. The United States Government does not endorse

products or manufacturers. Trade or manufacturer's names appear herein only

because they are considered essential to the objective of this document.



Technical Report Documentation Page

1. REPORT NO.

FHWA-NHI-07-092 2. GOVERNMENT

ACCESSION NO.

3. RECIPIENT'S CATALOG NO.

5. REPORT DATE

August 2008 4. TITLE AND SUBTITLE

Geosynthetic Design and

Construction Guidelines 6. PERFORMING ORGANIZATION CODE

7. AUTHOR(S) Robert D. Holtz, Ph.D., P.E., Barry R.

Christopher, Ph.D., P.E. and Ryan R. Berg, P.E.

8. PERFORMING ORGANIZATION REPORT NO.

10. WORK UNIT NO.9. PERFORMING ORGANIZATION NAME AND ADDRESS

Ryan R. Berg & Associates, Inc.

2190 Leyland Alcove

Woodbury, MN 55125

11. CONTRACT OR GRANT NO.

DTFH61-02-T-63036

13. TYPE OF REPORT & PERIOD COVERED12. SPONSORING AGENCY NAME AND ADDRESS

National Highway Institute

Federal Highway AdministrationU.S. Department of TransportationWashington, D.C.

14. SPONSORING AGENCY CODE

15. SUPPLEMENTARY NOTES

FHWA COTR – Larry Jones

FHWA Technical Consultants: Jerry A. DiMaggio, P.E. and Daniel Alzamora, P.E. This manual is the updated version of FHWA HI-95-038 (updated 1998) prepared by Ryan R. Berg & Associates,

Inc.; authored by R.D. Holtz, B.R. Christopher and R.R. Berg.

16. ABSTRACT This manual is an updated version of the FHWA Reference Manual for the NationalHighway Institute’s training courses on geosynthetic design and construction. The update was

performed to reflect current practice and codes for geosynthetics in highway works. The manual was prepared to enable the Highway Engineer to correctly identify and evaluate potential applications of

geosynthetics as alternatives to other construction methods and as a means to solve construction

problems. With the aid of this text, the Highway Engineer should be able to properly design, select,

test, specify, and construct with geotextiles, geocomposite drains, geogrids and related materials in

drainage, sediment control, erosion control, roadway, and embankment of soft soil applications.

Steepened reinforced soil slopes and MSE retaining wall applications are also addressed within, but

designers are referred to the more detailed FHWA NHI-00-043 reference manual on these subjects.

This manual is directed toward geotechnical, hydraulic, pavement, bridge and structures, construction,

maintenance, and route layout highway engineers, and construction inspectors and technicians

involved with design and/or construction and/or maintenance of transportation facilities that

incorporate earthwork.

17. KEY WORDS geosynthetics, geotextiles,

geogrids, geomembranes, geocomposites,

roadway design, filters, drains, erosion control,

sediment control, separation, embankments, soil

reinforcement

18. DISTRIBUTION STATEMENT

No restrictions.

19. SECURITY CLASSIF.

Unclassified 20. SECURITY CLASSIF.

Unclassified 21. NO. OF PAGES

59222. PRICE



SI CONVERSION FACTORS

APPROXIMATE CONVERSIONS FROM SI UNITS

Symbol When You

Know Multiply By To Find Symbol

LENGTH mm

mm

km

millimeters

metersmeters

kilometers

0.039

3.281.09

0.621

inches

feetyards

miles

in

ftyd

mi AREA

mm2 m2

m2

ha

km2

square millimeterssquare meters

square meters

hectares

square kilometers

0.001610.764

1.195

2.47

0.386

square inchessquare feet

square yards

acres

square miles

in2 ft2

yd2

ac

mi2 VOLUME

mll

m3

m3

millimetersliters

cubic meters

cubic meters

0.0340.264

35.71

1.307

fluid ouncesgallons

cubic feet

cubic yards

fl ozgal

ft3

yd3

MASS

gkg

tonnes

gramskilograms

tonnes

0.0352.202

1.103

ounces pounds

tons

ozlb

tons TEMPERATURE

EC Celsius 1.8 C + 32 Fahrenheit EF WEIGHT DENSITY

kN/m3

kilonewton / cubic

meter 6.36 poundforce / cubic foot pcf FORCE and PRESSURE or STRESS

NkN

kPa

kPa

newtonskilonewtons

kilopascals

kilopascals

0.225225

0.145

20.9

poundforce poundforce

poundforce / square inch

poundforce / square foot

lbflbf

psi

psf



FHWA NHI-07-092Geosynthetics Engineering i-1 August 2008

PREFACE

The 2007 update to the Geosynthetic Design & Construction Guidelines manual was initiated

to reflect the following recent publications:

• AASHTO Standard Specifications for Geotextiles — M 288; AASHTO, Standard

Specifications for Geotextiles - M 288, Standard Specifications for Transportation

Materials and Methods of Sampling and Testing, 26th

Edition, American Association

of State Transportation and Highway Officials, Washington, D.C., 2006.

• AASHTO, Geosynthetic Reinforcement of the Aggregate Base Course of Flexible

Pavement Structures – PP 46-0, Standard Specifications for Transportation Materials

and Methods of Sampling and Testing, 26th

Edition, and Provisional Standards,

American Association of State Transportation and Highway Officials, Washington,

D.C., 2006.

• Ground Improvement Methods, FHWA NHI-06-019 Volume I and FHWA NHI-06-

020 Volume II, 2006;

• Geotechnical Aspects of Pavements, FHWA-NHI-05-037, 2006;

• Development of Design Methods for Geosynthetic Reinforced Flexible Pavements,

FHWA DTFH61-01-X-00068, May 2004, 263p.;Available at: http://www.coe.montana.edu/wti/wti/pdf/426202_Final_Report.pdf

• NCHRP 1-37A Design Guide (2002). 2002 Design Guide – Design of New and

Rehabilitated Pavement Structures, Draft Final Report, Part 1 – Introduction and Part

2 – Design Inputs, Prepared for the National Cooperative Highway Research Program

by ERES Division of ARA.

• AASHTO Standard Specifications for Highway Bridges, Seventeenth Edition, 2002;

• Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and

Construction Guidelines , FHWA NHI-00-043, March 2001;

• Corrosion/Degradation of Soil Reinforcements for Mechanically Stabilized Earth

Walls and Reinforced Soil Slopes , FHWA NHI-00-044, March 2001;

• Geosynthetic Reinforcement of the Aggregate Base/Subbase Courses of Pavement

Structures B GMA White Paper II, Geosynthetic Materials Association, Roseville,

MN, 2000, 176 p.; and

• Geosynthetics in Pavement Systems Applications, Section One: Geogrids, Section

Two: Geotextiles, prepared for AASHTO, Geosynthetics Materials Association,

Roseville, MN, 1999, 46 p.



FHWA NHI-07-092Geosynthetics Engineering i- 2 August 2008

The 2007 revised Geosynthetic Design & Construction Guidelines manual evolved from the

following FHWA manuals:

• Geosynthetic Design & Construction Guidelines by Robert D. Holtz, Barry R.

Christopher, and Ryan R. Berg; Ryan R. Berg & Associates, Inc., FHWA HI-95-038;

1995 and updated in 1998; 460 p.

• Geotextile Design & Construction Guidelines - Participant Notebook by Barry R.

Christopher and Robert D. Holtz; STS Consultants, Northbrook, Illinois, and

GeoServices, Inc., Boca Raton, Florida; October 1988 and selectively updated to

April 1992.

• Geotextile Engineering Manual by Barry R. Christopher and Robert D. Holtz; STS

Consultants, Northbrook, Illinois; March, 1985; 917 p.

• Use of Engineering Fabrics in Transportation Type Related Applications by T. Allan

Haliburton, J.D. Lawmaster, and Verne C. McGuffey; 1981.

• Guidelines for Design, Specification, and Contracting of Geosynthetic Mechanically

Stabilized Earth Slopes on Firm Foundations; by Ryan R. Berg; Ryan R. Berg &

Associates, St. Paul, Minnesota; January, 1993; 88p.

• Reinforced Soil Structures - Volume I, Design and Construction Guidelines, and

Volume II Summary of Research and Systems Information; by B.R. Christopher, S.A.

Gill, J.P. Giroud, J.K. Mitchell, F. Schlosser, and J. Dunnicliff; STS Consultants,

Northbrook, Illinois, November 1990.

Special Acknowledgement

Jerry A. DiMaggio, P.E. is the FHWA Technical Consultant for this work, and served

in the same capacity for most of the above referenced publications. Mr. DiMaggio's

guidance and input to this and the previous works was invaluable.

The Geosynthetics Materials Association (GMA), the North American Geosynthetics

Society (NAGS), and the International Geosynthetics Society (IGS) provided support for this

revision. Their support to help initiate and to review this update is gratefully appreciated.




TABLE OF CONTENTS

1.0 INTRODUCTION............................................................................................................... 1-1

1.1 BACKGROUND ..................................................................................................... 1-11.2 DEFINITIONS, MANUFACTURING PROCESSES,

AND IDENTIFICATION.................................................................................... 1-2

1.3 FUNCTIONS AND APPLICATIONS.................................................................... 1-5

1.4 DESIGN APPROACH ............................................................................................ 1-9

1.5 EVALUATION OF PROPERTIES......................................................................... 1-9

1.6 SPECIFICATIONS................................................................................................ 1-21

1.7 FIELD INSPECTION............................................................................................ 1-24

1.8 FIELD SEAMING................................................................................................. 1-24

1.9 REFERENCES ...................................................................................................... 1-29

2.0 GEOSYNTHETICS IN SUBSURFACE DRAINAGE SYSTEMS ................................ 2-1

2.1 BACKGROUND ..................................................................................................... 2-1

2.2 APPLICATIONS..................................................................................................... 2-2

2.3 GEOTEXILE FILTER DESIGN - PRINCIPLES AND CONCEPTS .................... 2-4

2.4 FHWA FILTER DESIGN PROCEDURE............................................................... 2-8

2.4-1 Retention Criteria ..................................................................................... 2-8

2.4-2 Permeability and Permittivity Criteria.................................................... 2-10

2.4-3 Clogging Resistance ............................................................................... 2-12

2.4-4 Survivability and Durability Criteria...................................................... 2-15

2.4-5 Additional Filter Selection Considerations and Summary ..................... 2-16

2.5 DRAINAGE SYSTEM DESIGN GUIDELINES ................................................. 2-19

2.6 DESIGN EXAMPLE............................................................................................. 2-25

2.7 COST CONSIDERATIONS.................................................................................. 2-30

2.8 SPECIFICATIONS ............................................................................................... 2-31

2.9 INSTALLATION PROCEDURES ....................................................................... 2-36

2.10 FIELD INSPECTION........................................................................................... 2-37

2.11 IN-PLANE DRAINAGE; PREFABRICATEDGEOCOMPOSITE DRAINS............................................................................. 2-40

2.11-1 Design and Selection Criteria............................................................... 2-41

2.11-2 Construction Considerations................................................................. 2-44

2.12 REFERENCES .................................................................................................... 2-45




3.0 GEOTEXTILES IN RIPRAP REVETMENTS AND

OTHER PERMANENT EROSION CONTROL SYSTEMS .................................... 3-1

3.1 BACKGROUND ..................................................................................................... 3-1

3.2 APPLICATIONS ..................................................................................................... 3-2

3.3 DESIGN OF GEOTEXTILES BENEATH HARD ARMOR AND DESIGN

CONCEPTS ......................................................................................................... 3-4

3.3-1 Retention Criteria for Cyclic or Dynamic Flow ....................................... 3-4

3.3-2 Permeability and Effective Flow Capacity Requirements

for Erosion Control .................................................................................. 3-4

3.3-3 Clogging Resistance for Cyclic or Dynamic Flow and for Problematic

Soils.......................................................................................................... 3-5

3.3-4 Survivability Criteria for Erosion Control................................................ 3-5

3.3-5 Additional Filter Selection Considerations and Summary ....................... 3-6

3.4 GEOTEXTILE DESIGN GUIDELINES ................................................................ 3-9

3.5 GEOTEXTILE DESIGN EXAMPLE ................................................................... 3-15

3.6 GEOTEXTILE COST CONSIDERATIONS........................................................ 3-20

3.7 GEOTEXTILE SPECIFICATIONS ...................................................................... 3-21

3.8 GEOTEXTILE INSTALLATION PROCEDURES.............................................. 3-27

3.8-1 General Construction Considerations..................................................... 3-27

3.8-2 Cut and Fill Slope Protection.................................................................. 3-30

3.8-3 Streambank Protection............................................................................ 3-34

3.8-4 Precipitation Runoff Collection and Diversion Ditches ......................... 3-35

3.8-5 Wave Protection Revetments.................................................................. 3-36

3.8-6 Scour Protection ..................................................................................... 3-373.9 GEOTEXTILE FIELD INSPECTION .................................................................. 3-38

3.10 GEOCELLS ......................................................................................................... 3-38

3.11 EROSION CONTROL MATS ............................................................................ 3-39

3.11-1 Summary of Planning, Design, and Installation................................... 3-41

3.11-2 Specification .......................................................................................... 3-43

3.12 REFERENCES .................................................................................................... 3-44

4.0 TEMPORARY RUNOFF AND SEDIMENT CONTROL ............................................. 4-14.1 INTRODUCTION ................................................................................................... 4-1

4.2 FUNCTION OF SILT FENCES.............................................................................. 4-3

4.3 DESIGN OF SILT FENCES ................................................................................... 4-4

4.3-1 Estimates of Runoff and Sediment Volumes............................................ 4-5

4.3-2 Hydraulic Design of the Geotextile .......................................................... 4-6

4.3-3 Physical and Mechanical Properties; Constructability Requirements...... 4-7




4.4 SPECIFICATIONS.................................................................................................. 4-9


4.6 INSPECTION AND MAINTENANCE ................................................................ 4-13

4.7 SILT AND TURBIDITY CURTAINS.................................................................. 4-15

4.8 EROSION CONTROL BLANKETS .................................................................... 4-18

4.9 REFERENCES ...................................................................................................... 4-20

5.0 GEOSYNTHETICS IN ROADWAYS AND PAVEMENTS .......................................... 5-1

5.1 INTRODUCTION ................................................................................................... 5-1

5.2 APPLICABILITY AND BENEFITS OF GEOSYNTHETICS IN ROADWAYS . 5-2

5.2-1 Temporary Roads and Working Platforms............................................... 5-2

5.2-2 Permanent Paved and Unpaved Roads .................................................... 5-3

5.2-3 Subgrade Conditions in which Geosynthetics are Useful ........................ 5-4

5.2-4 Benefits..................................................................................................... 5-6

5.3 ROADWAY DESIGN USING GEOSYNTHETICS .............................................. 5-8

5.3-1 Functions of Geosynthetics in Roadways and Pavements........................ 5-8

5.3-2 Possible Failure Modes of Permanent Roads ......................................... 5-11

5.3-3 Design for Separation ............................................................................. 5-12

5.3-4 Design for Stabilization.......................................................................... 5-13

5.3-5 Reinforced Base/Subbase Design........................................................... 5-15

5.3-6 Material Properties used in Design......................................................... 5-16

5.4 DESIGN GUIDELINES FOR USE OF GEOTEXTILES IN TEMPORARY

AND UNPAVED ROADS ................................................................................ 5-21

5.4-1 Temporary Road Design Example ....................................................... 5-275.5 DESIGN GUIDELINES FOR USE OF GEOGRIDS IN TEMPORARY AND

UNPAVED ROADS.......................................................................................... 5-30

5.5-1 Empirical Design Method: Modified Steward et al............................. 5-30

5.5-2 Empirical Design Method of Giroud and Han...................................... 5-31

5.5-3 Design Example for Geogrid Reinforced Unpaved Road .................... 5-35

5.6 DESIGN GUIDELINES FOR USE OF GEOTEXTILES IN PERMANENT

PAVED ROADWAYS ...................................................................................... 5-42

5.6-1 Separation ............................................................................................. 5-42

5.6-2 Stabilization.......................................................................................... 5-425.6-3 Permanent Road Subgrade Stabilization Design Example................... 5-45

5.6-4 Improved Drainage ............................................................................... 5-49

5.7 DESIGN GUIDELINES FOR USE OF GEOGRIDS IN PERMANENT PAVED

ROADWAYS .................................................................................................... 5-52

5.7-1 Empirical Design Method from AASHTO PP46-01............................ 5-53

5.7-2 Mechanistic-Empirical Approach for Pavement Design ...................... 5-56


http:///reader/full/geosynthetic-design-construction-guidelines-nhi-course-no-132013-reference-manual-final-aug… 10/611


5.7-3 Design Example for Geogrid Reinforced Paved Roadway .................. 5-58


5.8-1 Roll Placement...................................................................................... 5-64

5.8-2a Geotextile Overlaps .............................................................................. 5-67

5.8-2b Geogrid Overlaps.................................................................................. 5-69

5.8-3 Seams.................................................................................................... 5-70

5.8-4 Field Inspection .................................................................................... 5-70

5.9 SPECIFICATIONS................................................................................................ 5-70

5.9-1 Geotextile for Separation and Stabilization Applications ...................... 5-70

5.9-2 Geogrids for Subgrade Stabilization....................................................... 5-76

5.9-3 Geosynthetics for Base Reinforcement of Pavement Structures ............ 5-80

5.10 COST CONSIDERATIONS................................................................................ 5-85

5.11 REFERENCES .................................................................................................... 5-86

6.0 PAVEMENT OVERLAYS ................................................................................................ 6-1

6.1 BACKGROUND ..................................................................................................... 6-1

6.2 PAVEMENT OVERLAYS AND REFLECTIVE CRACKING............................. 6-1

6.3 GEOTEXTILES....................................................................................................... 6-4

6.3-1 Functions .................................................................................................. 6-4

6.3-2 Asphalt Concrete (AC) Pavement Applications....................................... 6-5

6.3-3 Portland Cement Concrete Pavement Applications.................................. 6-6

6.3-4 HMAC-Overlaid PCC Pavements ............................................................ 6-7

6.3-5 Chip Seals for Unpaved Roads and AC Pavements ................................. 6-8

6.3-6 Advantages and Potential Disadvantages ................................................. 6-86.3-7 Design.................................................................................................... 6-10

6.3-8 Geotextile Selection................................................................................ 6-13

6.3-9 Cost Considerations................................................................................ 6-13

6.3-10 Specifications.......................................................................................... 6-16

6.3-11 Field Inspection ...................................................................................... 6-23

6.3-12 Recycling ................................................................................................ 6-23

6.4 GEOGRIDS ........................................................................................................... 6-24

6.4-1 Geogrid Functions .................................................................................. 6-24

6.4-2 Applications............................................................................................ 6-246.4-3 Design.................................................................................................... 6-25

6.4-4 Installation ............................................................................................. 6-26

6.4-5 Cost Considerations................................................................................ 6-26

6.4-6 Specifications.......................................................................................... 6-27

6.5 GEOCOMPOSITES .............................................................................................. 6-29

6.5-1 Membrane and Composite Strips ........................................................... 6-29




6.5-2 Specifications.......................................................................................... 6-30

6.6 REFERENCES ...................................................................................................... 6-31

7.0 REINFORCED EMBANKMENTS ON SOFT FOUNDATIONS ................................. 7-1

7.1 BACKGROUND ..................................................................................................... 7-1

7.2 APPLICATIONS..................................................................................................... 7-2

7.3 DESIGN GUIDELINES FOR REINFORCED EMBANKMENTS

ON SOFT SOILS ................................................................................................ 7-3

7.3-1 Design Considerations.............................................................................. 7-3

7.3-2 Design Steps ............................................................................................. 7-5

7.3-3 Comments on the Design Procedure ...................................................... 7-13

7.4 SELECTION OF GEOSYNTHETIC AND FILL PROPERTIES......................... 7-25

7.4-1 Geotextile and Geogrid Strength Requirements..................................... 7-26

7.4-2 Drainage Requirements .......................................................................... 7-28

7.4-3 Environmental Considerations ............................................................... 7-28

7.4-4 Constructability (Survivability) Requirements....................................... 7-28

7.4-5 Stiffness and Workability ....................................................................... 7-31

7.4-6 Fill Considerations.................................................................................. 7-33

7.5 DESIGN EXAMPLE............................................................................................. 7-33

7.6 SPECIFICATIONS................................................................................................ 7-40


7.8 CONSTRUCTION PROCEDURES...................................................................... 7-45

7.9 INSPECTION ........................................................................................................ 7-527.10 REINFORCED EMBANKMENTS FOR ROADWAY WIDENING ................ 7-52

7.11 REINFORCEMENT OF EMBANKMENTS COVERING LARGE AREAS.... 7-54

7.12 COLUMN SUPPORTED EMBANKMENTS .................................................... 7-54

7.13 REFERENCES .................................................................................................... 7-57

8.0 REINFORCED SLOPES ................................................................................................... 8-1

8.1 BACKGROUND ..................................................................................................... 8-1

8.2 APPLICATIONS..................................................................................................... 8-18.3 DESIGN GUIDELINES FOR REINFORCED SLOPES........................................ 8-4

8.3-1 Design Concepts ....................................................................................... 8-4

8.3-2 Design of Reinforced Slopes .................................................................... 8-5

8.3-3 Reinforced Slope Design Guidelines........................................................ 8-7

8.3-4 Computer Assisted Design ..................................................................... 8-27

8.4 MATERIAL PROPERTIES .................................................................................. 8-28




8.4-1 Reinforced Slope Systems...................................................................... 8-28

8.4-2 Soils ........................................................................................................ 8-28

8.4-3 Geosynthetic Reinforcement .................................................................. 8-30

8.5 TREATMENT OF OUTER FACE........................................................................ 8-33

8.6 PRELIMINARY DESIGN AND COST EXAMPLE............................................ 8-37


8.8 IMPLEMENTATION............................................................................................ 8-44

8.9 SPECIFICATIONS AND CONTRACTING APPROACH .................................. 8-46

8.9-1 Specification for Geosynthetic Soil Reinforcement ............................... 8-47

8.9-2 Specification for Geosynthetic Reinforced Soil Slope System .............. 8-53

8.10 INSTALLATION PROCEDURES ..................................................................... 8-55

8.11 FIELD INSPECTION.......................................................................................... 8-59

8.12 STANDARD DESIGNS...................................................................................... 8-59

8.13 REFERENCES .................................................................................................... 8-62

9.0 MECHANICALLY STABILIZED EARTH RETAINING

WALLS AND ABUTMENTS ....................................................................................... 9-1

9.1 BACKGROUND ..................................................................................................... 9-1

9.2 APPLICATIONS ..................................................................................................... 9-3

9.3 DESCRIPTION OF MSE WALLS ......................................................................... 9-5

9.3-1 Soil Reinforcements ................................................................................. 9-5

9.3-2 Facings...................................................................................................... 9-5

9.4 DESIGN GUIDELINES FOR MSE WALLS ....................................................... 9-10

9.4-1 Approaches and Models ......................................................................... 9-109.4-2 Design Steps .......................................................................................... 9-12

9.4-3 Comments on the Design Procedure ...................................................... 9-18

9.4-4 Drainage.................................................................................................. 9-30

9.4-5 Seismic Design ....................................................................................... 9-32

9.5 LATERAL DISPLACEMENT.............................................................................. 9-34

9.6 MATERIAL PROPERTIES .................................................................................. 9-34

9.6-1 Reinforced Wall Fill Soil........................................................................ 9-34

9.6-2 Geosynthetic Reinforcement .................................................................. 9-36

9.7 COST CONSIDERATIONS................................................................................. 9-439.8 COST ESTIMATE EXAMPLES ......................................................................... 9-44

9.8-1 Geogrid, MBW Unit-Faced Wall ........................................................... 9-44

9.8-2 Geotextile Wrap Wall............................................................................. 9-48

9.9 SPECIFICATIONS................................................................................................ 9-51

9.9-1 Geosynthetic, MBW Unit-Faced Wall ................................................... 9-51

9.9-2 Modular Block Wall Unit ....................................................................... 9-59




9.9-3 Geosynthetic Wrap Around Wall ........................................................... 9-66

9.10 CONSTRUCTION PROCEDURES.................................................................... 9-74

9.10-1 Concrete Faced Wall ............................................................................ 9-74

9.10-2 Geotextile Wrap-Around Wall ............................................................. 9-76

9.11 INSPECTION ...................................................................................................... 9-78

9.12 IMPLEMENTATION.......................................................................................... 9-80

9.12-1 Design Responsibility........................................................................... 9-81

9.12-2 Standardized Designs ........................................................................... 9-81

9.12-1 Geosynthetic Design Strength .............................................................. 9-85

9.13 SUMMARY OF LOAD RESISTANCE FACTOR DESIGN............................. 9-85

9.13-1 Introduction .......................................................................................... 9-85

9.13-2 Background........................................................................................... 9-86

9.13-3 MSE Wall Design................................................................................. 9-87

9.13-4 External Stability .................................................................................. 9-87

9.13-5 Internal Stability ................................................................................... 9-88

9.14 REFERENCES .................................................................................................... 9-89

10.0 GEOMEMBRANES AND OTHER GEOSYNTHETIC BARRIERS....................... 10-1

10.1 BACKGROUND ................................................................................................. 10-1

10.2 GEOSYNTHETIC BARRIER MATERIALS..................................................... 10-1

10.2-1 Geomembranes ..................................................................................... 10-2

10.2-2 Thin-Film Geotextile Composites ........................................................ 10-3

10.2-3 Geosynthetic Clay Liners ..................................................................... 10-4

10.2-4 Field-Impregnated Geotextiles ............................................................. 10-510.3 APPLICATIONS ................................................................................................. 10-5

10.4 DESIGN CONSIDERATIONS ......................................................................... 10-10

10.4-1 Performance Requirements................................................................. 10-11

10.4-2 In-Service Conditions ......................................................................... 10-11

10.4-3 Durability............................................................................................ 10-12

10.4-4 Installation Conditions........................................................................ 10-12

10.4-5 Peer Review........................................................................................ 10-14

10.4-6 Economic Considerations ................................................................... 10-14

10.5 INSTALLATION .............................................................................................. 10-1410.6 INSPECTION .................................................................................................... 10-15

10.6-1 Manufacture........................................................................................ 10-16

10.6-2 Field .................................................................................................... 10-16

10.7 SPECIFICATION.............................................................................................. 10-16

10.8 REFERENCES .................................................................................................. 10-17




APPENDICES

Appendix A — GEOSYNTHETIC LITERATURE

Appendix B — GEOSYNTHETIC TERMS

Appendix C — NOTATION AND ACRONYMS

Appendix D — AASHTO M288 SPECIFICATION

Appendix E — GEOSYNTHETIC TEST STANDARDS

E-1 American Society for Testing and Materials

E-2 Geosynthetic Research Institute

Appendix F — REPRESENTATIVE LIST OF GEOSYNTHETIC

MANUFACTURERS AND SUPPLIERS

Appendix G — GENERAL PROPERTIES AND COSTS OF GEOTEXTILES

AND GEOGRIDS

Appendix H — GEOSYNTHETIC REINFORCEMENT STRUCTURAL

DESIGN PROPERTIES

H.1 BACKGROUND

H.2 TENSILE STRENGTHS

H.3 REDUCTION FACTORS

H.4 IMPLEMENTATION

H.5 ALTERNATIVE LONG-TERM STRENGTH DETERMINATION

H.6 SOIL-REINFORCEMENT INTERACTION

H.7 REFERENCES




List of Tables

1-1 Representative Applications and Controlling Functions of Geosynthetics ......................... 1-7

1-2 Important Criteria and Principal Properties Required for Evaluation of Geosynthetics ... 1-111-3 Evaluation of Geosynthetic Property Requirements ......................................................... 1-12

1-4 Geosynthetic Properties and Parameters ........................................................................... 1-12

1-5 Geosynthetic Field Inspection Checklist ........................................................................... 1-25

2-1 Guidelines for Evaluating the Critical Nature or Severity

of Drainage and Erosion Control Applications.................................................... 2-4

2-2 Geotextile Strength Property Requirements for Drainage Geotextiles ............................. 2-15

3-1 Geotextile Strength Property Requirements for Permanent

Erosion Control Geotextiles................................................................................ 3-7

4-1 Limits of Slope Steepness and Length to Limit Runoff Velocity to 0.3 m/s ...................... 4-4

4-2 Physical Requirements for Temporary Silt Fence Geotextiles ............................................ 4-9

5-1 Application and Associated Functions of Geosynthetics in Roadway Systems.................. 5-6

5-2 Construction Survivability Ratings ................................................................................... 5-16

5-3 Geotextile Property Requirements for Stabilization Applications (CBR < 3)................... 5-18

5-4 Geotextile Property Requirements for Separation Applications (CBR > 3)...................... 5-19

5-5 Geogrid Survivability Property Requirements for

Stabilization and Base Reinforcement Applications.......................................... 5-20

5-6 Bearing Capacity Factors for Different Ruts and Traffic

Conditions Both With and Without Geosynthetics............................................ 5-23

5-7 Recommended mi Values for Modifying Structural Layer Coefficients of

Untreated Base and Subbase Materials in Flexible Pavements ......................... 5-50

5-8 Quality of Pavement Drainage .......................................................................................... 5-50

5-9 Recommended Values of Drainage Coefficient, Cd, for Rigid Pavement Design ............. 5-51

5-10 Qualitative Review of Reinforcement Application

Potential for Paved Permanent Roads................................................................ 5-555-11 Recommended Minimum Geotextile Overlap Requirements ......................................... 5-69

6-1 Paving Grade Geotextile Selection.................................................................................... 6-14




List of Figures

Figure 1-1 Classification of geosynthetics and other soil inclusions .................................... 1-4

Figure 1-2 Types of (a) stitches and (b) seams, according to Federal Standard No. 751a ;

and (c) improper seam placement ...................................................................... 1-28Figure 1-3 Bodkin connection of HDPE uniaxial geogrid .................................................. 1-29

Figure 2-1 Grain-size distribution for several soils ............................................................... 2-5

Figure 2-2 Filter bridge formation......................................................................................... 2-7

Figure 2-3 Definitions of clogging and blinding ................................................................... 2-7

Figure 2-4 U.S. Army Corps of Engineers gradient ratio test device.................................. 2-14

Figure 2-5 Flow chart summary of FHWA filter design procedure .................................... 2-18

Figure 2-6 Typical gradations and Darcy permeabilities of several aggregate and

graded filter materials ........................................................................................ 2-21

Figure 2-7 Construction procedure for geotextile-lined underdrains .................................. 2-37

Figure 2-8 Construction of geotextile drainage systems ..................................................... 2-38

Figure 2-9 Construction geotextile filters and separators beneath permeable

pavement base.................................................................................................... 2-39

Figure 2-10 Geocomposite drains.......................................................................................... 2-42

Figure 2-11 Prefabricated geocomposite edge drain construction using sand fill

upstream of composite ....................................................................................... 2-46

Figure 2-12 Recommended installation method for prefabricated geocomposite

edge drains ......................................................................................................... 2-47

Figure 3-1 Flow chart summary of FHWA filter design procedure ...................................... 3-8

Figure 3-2 Erosion control installations: a) installation in wave protection revetment;

b) river shoreline application; and c) stream application................................... 3-28

Figure 3-3 Construction of hard armor erosion control systems ......................................... 3-31

Figure 3-4 Special construction requirements related to specific hard armor erosion

control applications............................................................................................ 3-32

Figure 3-5 Recommended maximum design velocities and flow durations for erosion

resistance of various surface materials and treatments...................................... 3-42

Figure 4-1 Geotextile strength versus post spacing............................................................... 4-7

Figure 4-2 Post requirements versus post spacing................................................................. 4-8

Figure 4-3 Typical silt fence installation............................................................................. 4-14

Figure 4-4 Installation of a prefabricated silt fence............................................................. 4-15

Figure 4-5 Recommended maximum design velocities and flow durations for various

classes of erosion control materials .................................................................... 4-19




Figure 5-1 Potential applications of geosynthetics in a layered pavement system................ 5-2

Figure 5-2 Geotextile separator beneath permeable base ...................................................... 5-5

Figure 5-3 Concept of geotextile separation in roadways ..................................................... 5-9

Figure 5-5 Filtration at the interface of two dissimilar materials (without geosynthetics) . 5-14

Figure 5-6 U.S. Forest Service thickness design curve for single wheel load..................... 5-25

Figure 5-7 U.S. Forest Service thickness design curve for tandem wheel load .................. 5-25

Figure 5-8 Thickness design curves with geosynthetics for a) single and b) dual wheel

loads (modified for highway applications) ........................................................ 5-26

Figure 5-9 Aggregate loss to weak subgrades ..................................................................... 5-44

Figure 5-10 Mechanistic-Empirical (M-E) Pavement Design Method showing a) M-E

concept, and b) modified response model for inclusion of reinforcement ........ 5-56

Figure 5-11 Construction sequence using geosynthetics....................................................... 5-65

Figure 5-12 Forming curves using geotextiles ...................................................................... 5-68

Figure 5-13 Repair of rutting with additional material.......................................................... 5-69

Figure 6-1 Shearing and bending stress in HMA overlay ..................................................... 6-2

Figure 6-2 Geotextiles (a.k.a. Paving Fabric) in rehabilitated pavement section.................. 6-4

Figure 6-3 Relationship between the vertical compressive strain at the top of the

subgrade and the number of load applications in geogrid reinforced pavement6-25

Figure 7-1 Reinforced embankment applications.................................................................. 7-3

Figure 7-2 Reinforced embankments failure modes.............................................................. 7-4

Figure 7-3 Reinforcement required to provide rotational stability...................................... 7-10

Figure 7-4 Reinforcement required to limit lateral embankment spreading........................ 7-11Figure 7-5 Embankment height versus undrained shear strength of foundation ................. 7-16

Figure 7-6 Local bearing failure (lateral squeeze)............................................................... 7-17

Figure 7-7 Construction sequence for geosynthetic reinforced embankments for

extremely weak foundations .............................................................................. 7-48

Figure 7-8 Placement of fill between toe berms on extremely soft foundations

(CBR < 1) with a mud wave anticipated............................................................ 7-49

Figure 7-9 Fill placement to tension geotextile on moderate ground conditions ................ 7-50

Figure 7-10 Reinforced embankment construction ............................................................... 7-51

Figure 7-11 Reinforced embankment construction for roadway widening........................... 7-53Figure 7-12 Column supported embankment with geosynthetic reinforcement ................... 7-56

Figure 8-1 Use of geosynthetics in engineered slopes........................................................... 8-2

Figure 8-2 Applications of RSSs: .......................................................................................... 8-3

Figure 8-3 Requirements for design of a reinforced slope .................................................... 8-8

Figure 8-4 Critical zone defined by rotational and sliding surface that meet the




required safety factor ......................................................................................... 8-10

Figure 8-5 Rotational shear approach to determine required strength of reinforcement..... 8-12

Figure 8-6 Sliding wedge approach to determine the coefficient of earth pressure K ........ 8-14

Figure 8-7 Spacing and embedding requirements for slope reinforcement showing:

primary and intermediate reinforcement layout................................................. 8-16

Figure 8-8 Developing reinforcement length ...................................................................... 8-18

Figure 8-9 Cost evaluation of reinforced soil slopes ........................................................... 8-44

Figure 8-10 Construction of reinforced slopes ...................................................................... 8-57

Figure 8-11 Reinforced slope construction............................................................................ 8-58

Figure 8-12 Example of standard design ............................................................................... 8-61

Figure 9-1 Component parts of a Reinforced Earth wall....................................................... 9-2

Figure 9-2 Reinforced retaining wall systems using geosynthetics....................................... 9-3

Figure 9-3 Examples of geosynthetic MSE walls.................................................................. 9-4

Figure 9-4 Possible geosynthetic MSE wall facings ............................................................. 9-6

Figure 9-5 Wall facings ......................................................................................................... 9-8

Figure 9-6 Actual geosynthetic reinforced soil wall in contrast to the design model ......... 9-11

Figure 9-7 Geometric and loading characteristics of geosynthetic MSE walls................... 9-14

Figure 9-8 Example MSE wall drainage blanket detail....................................................... 9-32

Figure 9-9 Drainage details for MBW faced, MSE wall ..................................................... 9-33

Figure 9-10 Polyethylene geogrid bodkin connection detail ................................................. 9-39

Figure 9-11 Example MBW mechanical connection............................................................. 9-39

Figure 9-12 Cost comparison of reinforced systems ............................................................. 9-44Figure 9-13 Lift construction sequence for geotextile reinforced soil walls ......................... 9-79

Figure 9-14 Typical face construction detail for vertical geogrid-reinforced

retaining wall faces ............................................................................................ 9-80

Figure 9-15 Example of standard MSE wall design.............................................................. 9-83

Figure 9-16 Typical application of live load surcharge for MSE walls ................................ 9-88

Figure 10-1 Thin-film geotextile composites ........................................................................ 10-4

Figure 10-2 Geosynthetic clay liners..................................................................................... 10-4

Figure 10-3 Control of expansive soils.................................................................................. 10-7Figure 10-4 Control of horizontal infiltration of base ........................................................... 10-7

Figure 10-5 Maintenance of optimum water content ............................................................ 10-8

Figure 10-6 Waterproofing of tunnels ................................................................................... 10-8

Figure 10-7 Water conveyance canals................................................................................... 10-9

Figure 10-8 Secondary containment of underground fuel tanks ........................................... 10-9

Figure 10-9 Waterproofing of walls ................................................................................... 10-10



FHWA NHI-07-092 Introduction, Identification, and EvaluationGeosynthetics Engineering 1-1 August 2008

1.0 INTRODUCTION

1.1 BACKGROUND

The objective of this manual is to assist highway design engineers, specification writers,

estimators, construction inspectors, and maintenance personnel with the design, selection,

and installation of geosynthetics. In addition to providing a general overview of these

materials and their applications, step-by-step procedures are given for the cost-effective use

of geosynthetics in drainage and erosion control systems, roadways, reinforced soil

structures, and in containment applications. Although the title refers to the general term

geosynthetic, the appropriate use of the subfamilies of geotextiles, geogrids, geocomposites,

and geomembranes are discussed in specific applications.

The basis for much of this manual is the FHWA Geotextile Engineering Manual (Christopher

and Holtz, 1985). Other sources of technical information include the book by Koerner

(2006) and a number of FHWA reports and publications. If you are not already somewhat

familiar with geosynthetics, you are encouraged to read the books by Ingold and Miller

(1988), Richardson and Koerner (1990), and Fannin (2000). Additional references are in the

geosynthetic bibliographies prepared by Giroud (1993, 1994).

Geosynthetics terminology is defined in Appendix B and ASTM (2006) D 4439 “Standard

Terminology for Geosynthetics”. Common notation and symbols are used throughout this

manual, and for easy reference a list is provided in Appendix C. The notation and symbolsare generally consistent with the International Geosynthetic Society's (IGS) Recommended

Mathematical and Graphical Symbols (2000).

Sample specifications for each primary application are also included in this manual.

Remember that these specifications are only guidelines and should be modified as

required by project specific design and performance criteria, engineering judgment,

and experience. For the more routine highway applications, specifications are adapted from

the American Association of State Highway and Transportation Officials (AASHTO)

Standard Specification, Designation M 288 (2006). (The AASHTO M 288 specification can be found in Appendix D.) Other sample specifications were provided by New York and

Washington DOTs, the National Concrete Masonry Association, and the FHWA.

Historically, the AASHTO M 288 specifications were based on a geotextile specification

originally developed by Task Force 25 of the Joint Subcommittee on Materials of AASHTO,

the Association General Contractors (AGC), and the American Road and Transportation

Builders Associations (ARTBA), along with representatives from the geosynthetic industry




(AASHTO, 1990a). Another important early group was Task Force 27 on soil reinforcing,

sponsored by the same AASHTO-AGC-ARTBA Subcommittee on Materials (AASHTO,

1990b). The FHWA soil reinforcing specifications for walls and slopes are from Elias et al.

(2001).

In this introductory chapter, we define geosynthetics and discuss what they are made of, how

they are made, and how they should be identified. Then we introduce you to the functions

and applications of geosynthetics, and we describe in some detail the methods used to

evaluate their engineering properties. Finally, we provide some general comments about

design, construction, and inspection that apply to all applications.

The remaining chapters of this manual provide specific details about the major application

categories. Each chapter provides a step-by-step systematic approach to design, a design

example, cost considerations, sample specifications, installation procedures, and inspection

suggestions. Proper attention to these details will ensure successful and cost-effective

geosynthetic designs and installations.

1.2 DEFINITIONS, MANUFACTURING PROCESSES, AND IDENTIFICATION

ASTM (2006) D 4439 defines a geosynthetic as a planar product manufactured from a

polymeric material used with soil, rock, earth, or other geotechnical-related material as an

integral part of a civil engineering project, structure, or system. The first to be developed and

most widely used geosynthetic is a geotextile, defined by ASTM as a permeable geosyntheticcomprised entirely of textiles. A number of other geosynthetics are available, including grids,

membranes, nets, meshes, webs, and composites; that are used in combination with or in

place of geotextiles. Geogrids are formed by a regular network of tensile elements with

apertures of sufficient size to interlock with surrounding fill material. Geogrids are primarily

used for reinforcement, geomembranes are low-permeability geosynthetics used as fluid

barriers. Geotextiles and other geosynthetics such as nets and grids can be combined with

geomembranes and other geosynthetics to provide the best attributes of each material. These

products are called geocomposites, and they include geotextile-geonets, geotextile-geogrids,

geotextile-geomembranes, geomembrane-geonets, geotextile-polymeric cores, and eventhree-dimensional polymeric cell structures.

A convenient classification scheme for geosynthetics is provided in Figure 1-1. Most

geosynthetics are made from synthetic polymers, and of these, polypropylene, polyester, and

polyethylene are by far the most common. These polymers are normally highly resistant to

biological and chemical degradation. Less-frequently-used polymers include polyamides




(e.g., nylon, which is not very durable in soil because it softens in the presence of water),

polyvinyl chloride (PVC), and glass fibers. Natural fibers such as cotton, jute, etc., could

also be used to make materials that are similar to geotextiles. Because these products are

biodegradable, they are only for temporary applications. Natural fiber geotextile-related

materials have not been widely utilized in the U.S. For additional information about the

polymeric composition of geosynthetics, see Koerner (2006).

In manufacturing geotextiles, basic elements such as fibers or yarns are combined into planar

textile structures. The fibers can be continuous filaments, which are very long thin strands of

a polymer, or staple fibers, which are short filaments, typically ¾ to 6 in. (20 to 150 mm)

long. Sometimes an extruded plastic sheet or film is slit to form thin, flat tapes. With both

continuous filaments and slit tapes, the extrusion or drawing process elongates the polymers

in the direction of the draw and increases the strength of the filament or tape. After the

drawing process, filaments and tapes may also be fibrillated, a process in which the filaments

are split into finer filaments by crimping, twisting, cutting or nipped with a pinned roller.

This process provides pliable, multifilament yarns with a more open structure that are easier

to weave.

Geotextile type is determined by the method used to combine the filaments or tapes into the

planar structure. The vast majority of geotextiles are either woven or nonwoven. Woven

geotextiles are made of monofilament , multifilament , or fibrillated yarns, or of slit film tapes.

The weaving process is as old as Homo Sapiens' have been making clothing and textiles.

Nonwoven textile manufacture is a modern development, a “high-tech” process industry, in

which synthetic polymer fibers or filaments are continuously extruded and spun, blown orotherwise laid onto a moving conveyor belt. Then the mass of filaments or fibers are either

needlepunched , in which the filaments are mechanically entangled by a series of small

needles, or heat bonded, in which the individual fibers are welded together by heat and

pressure at their points of contact in the nonwoven mass.

Geogrids with integral junctions are manufactured by extruding and orienting sheets of

polyolefins (polyethylene or polypropylene). These types of geogrids are often called

extruded or integral geogrids. Geogrids may also be manufactured of multifilament

polyester yarns, joined at the crossover points by a knitting or weaving process, and thenencased with a polymer-based, plasticized coating. These types of geogrids are often called

woven or flexible geogrids. A third type, a welded geogrid manufactured, as the name

implies, by welding polymeric strips (e.g., strapping material) together at their cross over

points. All these manufacturing techniques allow geogrids to be oriented such that the

principal strength is in one direction, called uniaxial geogrids, or in both directions (but not

necessarily the same), called biaxial geogrids.




The manufacture of other geosynthetic products is as varied as the products themselves.

Geonets, geosynthetic erosion mats, geowebs, geomeshes, etc., can be made from large and

often rather stiff filaments formed into a mesh with integral junctions or they can be welded

or glued at the crossover points. Manufacture of geomembranes and other geosynthetic

barriers is discussed in Chapter 10.

Geocomposites result when two or more geosynthetics are combined in the manufacturing

process. Most geocomposites are used in drainage applications and waste containment. A

common example of a geocomposite is a prefabricated drain that consists of a fluted or

dimpled polymeric sheet, which acts as a conduit for water, wrapped with a geotextile that

acts as a filter.

TEXTILES WEBBINGS

SYNTHETIC NATURAL SYNTHETIC NATURALVarious polymers SteelPolymers

Palm wood

WoodBamboo

Polypropylene

Polyethylene

Polyester, etc.

Cotton

JuteReeds

Grass

IMPERMEABLE PERMEABLE CLOSE-MESH OPEN MESH

Geomembrane polymers:

Nets

Mats

Geogrids

Bar mats

Combination

Products

SHEETS STRIPS

Polyethylene (HDPE, LLDPE, etc.)

Polyvinyl Chloride (PVC)

Cholosulphonated Polyethylene (CSPE)

Ethylene Interpolymer Alloy (EIA)Rubber, etc.

Formed Plasticwith pins, etc.

Reinforced EarthYork System

GEOTEXTILES

NONWOVEN KNITTED WOVENContinuous Filament

Staple FilamentCombination Products

(Geocomposites)

NEEDLE-

PUNCHED

CHEMICAL

BONDED

HEAT-

BONDED

SpunbondedWet Laid

Resin Bonded

MONOFILAMENT

YARNS

SLIT FILM

YARNS

FIBRILLATED

YARNS

MULTIFILAMENT

YARNS Noncalendered

Calendered

Noncalendered

Calendered

Figure 1-1. Classification of geosynthetics and other soil inclusions (modified after

Rankilor, 1981).




include dissipation of pore water pressures at the base of roadway embankments. For

situations with higher flow requirements, for example, pavement edge drains, slope

interceptor drains, and retaining wall drains, geocomposite drains are often used. Filtration,

drainage, and erosion control are addressed in Chapters 2, 3, and 4.

Geotextiles are often used as separators to prevent road base materials from penetrating into

the underlying soft subgrade, thus maintaining the design thickness and roadway integrity.

Separators also prevent fine-grained subgrade soils from being pumped into permeable,

granular road bases. Separators are discussed in Chapter 5.

Both geotextiles and geogrids can be used as reinforcement to add tensile strength to a soil

matrix, thereby providing a more competent and stable material. Reinforcement enables

embankments to be constructed over very soft foundations and permits the construction of

steep slopes and retaining walls. Reinforcement applications are presented in Chapters 7, 8,

and 9. Geogrids and geotextiles can also be used as reinforcement in roadway base and

subbase aggregate layers to improve the performance of pavement systems as discussed in

Chapter 5.

Geomembranes, thin-film geotextile composites, geosynthetic clay liners, and field-coated

geotextiles are used as fluid barriers to impede the flow of a liquid or gas from one location

to another. This geosynthetic function has wide application in asphalt pavement overlays,

encapsulation of swelling soils, and waste containment. Pavement overlays are discussed in

Chapter 6. Geomembranes and other geosynthetic barriers are described in Chapter 10.

The sixth function is, protection, in which the geosynthetic acts as a stress relief layer.

Temporary geosynthetic blankets and permanent geosynthetic mats are placed over the soil to

reduce erosion caused by rainfall impact and water flow shear stress. A protective cushion of

nonwoven geotextiles is often used to prevent puncture of geomembranes (by reducing point

stresses) from stones in the adjacent soil or drainage aggregate during installation and while

in service as discussed in Chapter 10. Geotextiles also provide stress relief to retard the

development of reflection cracks in pavement overlays as discussed in Chapter 6

In addition to the primary function, geosynthetics usually perform one or more secondary functions. The primary and secondary functions make up the total contribution of the

geosynthetic to a particular application. A listing of common applications according to

primary and secondary functions is presented in Table 1-1. Secondary functions can be

equally important as the primary function, and in order to obtain optimum geosynthetic

performance, both much be considered in the design computations and specifications.




Table 1-1

Representative Applications and

Controlling Functions of Geosynthetics

PRIMARYFUNCTION APPLICATION SECONDARY FUNCTION(S)

Separation Unpaved Roads (temporary & permanent)

Paved Roads (secondary & primary)

Construction Access RoadsWorking Platforms

Railroads (new construction)

Railroads (rehabilitation)

Landfill CoversPreloading (stabilization)

Marine Causeways

General Fill AreasPaved & Unpaved Parking Facilities

Cattle CorralsCoastal & River Protection

Sports Fields

Filter, drains, reinforcement

Filter, drains

Filter, drains, reinforcementFilter, drains, reinforcement



Reinforcement, drains, protectionReinforcement, drains




Filter, drains, protection

Filter Trench Drains

Pipe Wrapping

Base Course Drains

Frost Protection

Structural DrainsToe Drains in Dams

High Embankments

Filter Below Fabric-FormSilt Fences

Silt Screens

Culvert OutletsReverse Filters for Erosion Control:

Seeding and Mulching

Beneath Gabions

Ditch Armoring

Embankment Protection, CoastalEmbankment Protection, Rivers

& Streams

Embankment Protection, LakesVertical Drains (wicks)

Separation, drains

Separation, drains, protection

Separation, drains

Separation, drainage, reinforcement

Separation, drainsSeparation, drains

Drains

Separation, drainsSeparation, drains

Separation

SeparationSeparation

Drainage-Transmission Retaining Walls

Vertical Drains

Horizontal DrainsBelow Membranes (drainage of gas and

water)

Earth DamsBelow Concrete (decking & slabs)

Separation, filter

Separation, filter

ReinforcementReinforcement, protection

FilterProtection




Table 1-1

Representative Applications and

Controlling Functions of Geosynthetics(continued)

PRIMARY

FUNCTIONAPPLICATION SECONDARY FUNCTION(S)

Reinforcement Pavement Overlays

Subbase Reinforcement in Roadways &

Retaining Structures

Membrane SupportEmbankment Reinforcement

Fill Reinforcement

Foundation SupportSoil Encapsulation

Net Against Rockfalls

Fabric Retention SystemsSand Bags

Reinforcement of Membranes

Load Redistribution

Bridging Nonuniformity Soft Soil Areas

Encapsulated Hydraulic FillsBridge Piles for Fill Placement

----------

Filter

DrainsSeparation, drains, filter, protection

Drains

DrainsDrains

Drains, filter, separation

DrainsDrains

----------

Protection

Separation

SeparationSeparation

----------

Fluid Barrier Asphalt Pavement Overlays

Liners for Canals and Reservoirs

Liners for Landfills and Waste

Repositories

Covers for Landfill and WasteRepositories

Cutoff Walls for Seepage Control

Waterproofing TunnelsFacing for Dams

Membrane Encapsulated Soil Layers

Expansive Soils

Flexible Formwork

Protection

----------

----------

----------

--------------------

----------

--------------------

----------

----------

----------

Protection Geomembrane Cushion

Asphalt Overlay

Temporary Erosion Control

Permanent Erosion Control

Drains

Fluid barrier

Fluid barrier

Reinforcement, fluid barrier




1.4 DESIGN APPROACH

Considering the wide variety of geosynthetics available, engineering based on the specific

project conditions and constraints is required in order to obtain the most suitable material for

any application. We recommend the following approach to designing with geosynthetics:

1. Define the purpose and establish the scope of the project.

2. Investigate and establish the geotechnical conditions at the site (geology, subsurface

exploration, laboratory and field testing, etc.).

3. Establish application criticality, severity, and performance criteria. Determine

external factors that may influence the geosynthetic's performance.

4. Formulate trial designs and compare several alternatives.

5. Establish the models to be analyzed, determine the parameters, and carry out the

analysis.

6. Compare results and select the most appropriate design; consider alternatives versus

cost, construction feasibility, etc. Modify the design if necessary.

7. Prepare detailed plans and specifications including: a) specific property requirements

for the geosynthetic; and b) detailed installation procedures.

8. Hold preconstruction meeting with contractor and inspectors.

9. Approve geosynthetic on the basis of specimens' laboratory test results and/or

manufacturer's certification.

10. Monitor construction.

11. Inspect after major events (e.g., 100 year rainfall or an earthquake) that may

compromise system performance.

By following this systematic approach to design and installation of geosynthetics, cost-

effective designs can be achieved, along with improved performance, increased service life,

and reduced maintenance costs. Good communication and interaction between all concerned

parties is imperative throughout the design and selection process.

1.5 EVALUATION OF PROPERTIES

Today, there are more than 600 different geosynthetic products available in North America.

Because of the wide variety of products, with their different polymers, filaments, weaving (or

nonwoven) patterns, bonding mechanisms, thicknesses, masses, etc., they have a

considerable range of physical and mechanical properties. Thus, the process of comparison

and selection of geosynthetics is not easy. Geosynthetic testing has progressed significantly

since the FHWA Geotextile Engineering Manual (Christopher and Holtz, 1985) was




published. Specific test procedures for most geosynthetic properties can be found in ASTM

(2006). These procedures have been developed by ASTM Committee D 35 on Geosynthetics

during the past 20 years or so. Because ASTM standards are consensus standards, the

process is often slow, and to help speed up the process, the Geosynthetics Research Institute

(GRI) of Drexel University has issued interim standards for a number of tests. They are only

active until an equivalent ASTM standard is adopted. ASTM (2006) and GRI (2006)

standards are listed in Appendix E. Note that test procedures referred to in the AASHTO

standard Geotextile Specification for Highway Applications, Designation M 288, are

primarily ASTM standard test procedures.

The particular, required design properties of the geosynthetic will depend on the specific

application and the associated function(s) the geosynthetic is to provide. The properties

listed in Table 1-2 cover the range of important criteria and properties required to evaluate a

geosynthetic for most applications in this manual. It should be noted that not all of the listed

requirements will be necessary for all applications. Typically only six to eight properties are

required for a specific application. Also note that in Table 1-2, properties required for

mechanical or hydraulic design are different than those required for constructability

(sometimes called survivability) and longevity or durability.

Table 1-3 lists all the geosynthetics applications included in this manual along with their

associated functions. Use Table 1-3 along with Tables 1-1 and 1-2 to determine the

appropriate properties for each application.

All current geosynthetic properties and parameters are listed in Table 1-4, along with theASTM or GRI test procedures for each property and their preferred units of measurement.

All geosynthetic properties can be placed into three basic categories: general, index, and

performance properties. General properties, given in Table 1-4, are usually provided by the

manufacturers or their distributors. Another source of general properties is the Specifier's

Guide published each December in the Geosynthetics magazine (formerly Geotechnical

Fabrics Report), published by the Industrial Fabrics Association International (IFAI). In

addition to general and some index properties for most product types and manufacturers, the

Specifier's Guide also contains a directory of manufacturers, distributors, installers, design

engineers, and testing laboratories. Contact information and web addresses are also provided.




Table 1-4 also lists index tests and performance tests. Index tests were originally developed

by manufacturers for quality control purposes, and as the name implies, they give only an

indication or a qualitative assessment of the property of interest. With some exceptions,

index test values are not appropriate for design, although when determined using standard

test procedures, index properties can be used for product comparison, procurement

specifications, and quality control of construction and installation.

Table 1-2

Important Criteria and Principal

Properties Required for Evaluation of Geosynthetics

FUNCTION

CRITERIA AND

PARAMETER

PROPERTY1 Filtration Drainage Separation Reinforcement Barrier Protection

Design Requirements:

Mechanical Strength

Tensile Strength Wide Width Strength — — — —

Tensile Modulus Wide Width Modulus — — — —

Seam Strength Wide Width Strength — — — —

Tension Creep Creep Resistance — — — —Compression Creep Creep Resistance — 2 — — — —

Soil-Geosynthetic

Friction

Shear Strength — — —

Hydraulic

Flow Capacity Permeability —

Transmissivity — — — —

Piping Resistance Apparent Opening Size — —

Porimetry — — — —

Clogging Resistance Gradient Ratio or Long-

Term Flow

— — — —

Constructability

Requirements:

Tensile Strength Grab Strength

Seam Strength Grab Strength — —

Bursting Resistance Burst Strength

Puncture Resistance Rod or Pyramid

Puncture

Tear Resistance Trapezoidal Tear

Longevity (Durability):

Abrasion Resistance3 Reciprocating Block

Abrasion

— — — — —

UV Stability4 UV Resistance — —

Soil Environment5 Chemical ? ?

Biological

?

?Wet-Dry — — —

Freeze-Thaw — — —

NOTES

1. See Table 1-4 for specific procedures.2. Compression creep is applicable to some geocomposites.

3. Erosion control applications where armor stone may move.

4. Exposed geosynthetics only.

5. Where required.

Documents

Geosynthetic Design & Construction Guidelines NHI Course No. 132013-Reference-Manual-Final-August-2008