100 to 150 RSS projects are being constructed yearly in connection with transportationrelated projects in the United States, with an estimated projected vertical face area of2,000,000 ft2/year (190,000m2/yr)Table 1-2-RepresentativeList of Geogrid and Geotextile Reinforcement Suppliers.ACEGeosynthetics EnterpriseCo.,Ltd.Belton Industries Inc.No.8Kung 10 Rd5600OakbrookPkwySte150Yu-Shih Ind. Park, TachiaNorcross, GA30093-1843Taichung43768www.beltonindustries.comTaiwanwww.geoace.comCarthage MillsCheckmate Geosynthetics Inc.4243Hunt RdUnit#41244500SouthSumasRd.Cincinnati, OH45242-6645Chilliwack, BCV2R5M3Canadawww.carthagemills.comwww.checkmategeogrid.comColbond Inc.FiberwebPLCPOBox105770 Old Hickory Blvd.1301 Sand HillRdOld Hickory,TN 37138Enka, NC 28728-1057www.fiberweb.comwww.colbond.comDalco NonwovensGeo-Synthetics Inc.PO Box 14792401PewaukeeRd2050 Evergreen Dr NeWaukesha,WI53188Conover, NC 28613-1479www.geo-synthetics.comwww.dalcononwovens.comGSE Lining Technology IncHighland Industries Inc19103GundleRd629 Green Valley Rd., Suite 210Houston, TX 77073-3515Greensboro, NC27408www.gseworld.comwww.highlandindustries.comHuesker Inc.Layfield Plastics Inc.POBox41152911603180thStSWCharlotte,NC28241-1529Edmonton, AB T5S 2H6www.hueskerinc.comCanadawww.layfieldgroup.comMaccaferri Inc.Luckenhaus Technical Textiles Inc.3130Bee Tree Ln10303 Governor Lane BlvdSignal Mountain, TN 37377-1441Williamsport, MD 21795-3115www.maccaferri-usa.comNAUE America Inc.PropexGeosynthetics3525PiedmontRdNE6025LeeHighway,Ste.4257PiedmontCenterSte300P.O. Box 22788Atlanta, GA 30305-1578Chattanooga, TN 37422www.naue.comwww.propexinc.comSaint-Gobain Technical FabricsSKAPS Industries1795Baseline Rd335Athena DrGrand Island,NY14072-2010Athens, GA 30601www.glasrid.comwww.nevown.comFHWA NHI-10-0241- Introduction1-11MSE Walls and RSS-VolINovember2009
100 to 150 RSS projects are being constructed yearly in connection with transportation related projects in the United States, with an estimated projected vertical face area of 2,000,000 ft2 /year (190,000 m2 /yr). Table 1-2 – Representative List of Geogrid and Geotextile Reinforcement Suppliers. ACE Geosynthetics Enterprise Co., Ltd. No. 8 Kung 10 Rd. Yu-Shih Ind. Park, Tachia Taichung 43768 Taiwan www.geoace.com Belton Industries Inc. 5600 Oakbrook Pkwy Ste 150 Norcross, GA 30093-1843 www.beltonindustries.com Carthage Mills Checkmate Geosynthetics Inc. 4243 Hunt Rd Unit# 412 44500 South Sumas Rd. Cincinnati, OH 45242-6645 Chilliwack, BC V2R 5M3 www.carthagemills.com Canada www.checkmategeogrid.com Colbond Inc. Fiberweb PLC PO Box 1057 70 Old Hickory Blvd. 1301 Sand Hill Rd Old Hickory, TN 37138 Enka, NC 28728-1057 www.fiberweb.com www.colbond.com Dalco Nonwovens PO Box 1479 2050 Evergreen Dr Ne Conover, NC 28613-1479 www.dalcononwovens.com Geo-Synthetics Inc. 2401 Pewaukee Rd Waukesha, WI 53188 www.geo-synthetics.com GSE Lining Technology Inc. 19103 Gundle Rd Houston, TX 77073-3515 www.gseworld.com Highland Industries Inc 629 Green Valley Rd., Suite 210 Greensboro, NC 27408 www.highlandindustries.com Huesker Inc. PO Box 411529 Charlotte, NC 28241-1529 www.hueskerinc.com Layfield Plastics Inc. 11603 180th St SW Edmonton, AB T5S 2H6 Canada www.layfieldgroup.com Luckenhaus Technical Textiles Inc. 3130 Bee Tree Ln Signal Mountain, TN 37377-1441 Maccaferri Inc. 10303 Governor Lane Blvd Williamsport, MD 21795-3115 www.maccaferri-usa.com NAUE America Inc. 3525 Piedmont Rd NE 7 Piedmont Center Ste 300 Atlanta, GA 30305-1578 www.naue.com Propex Geosynthetics 6025 Lee Highway, Ste. 425 P.O. Box 22788 Chattanooga, TN 37422 www.propexinc.com Saint-Gobain Technical Fabrics 1795 Baseline Rd Grand Island, NY 14072-2010 www.glasrid.com SKAPS Industries 335 Athena Dr Athens, GA 30601 www.nevown.com FHWA NHI-10-024 1 – Introduction MSE Walls and RSS – Vol I 1 – 11 November 2009
Strata Systems, Inc., Div. Glen Raven, Inc.SynTeen Technical FabricsPOBox7911950WMeetingStStatesville,NC28687-0791Lancaster,SC29720-8811www.geogrid.comwww.synteen.comTenax Corp.TenCate Geosynthetics4800EMonument St365SHollandDrPendergrass, GA 30567-4625Baltimore,MD21205-3031www.tencate.comTensarInternationalCorporationThrace-LINQ Inc.5883GlenridgeDrNESte2002550W5thNorthStAtlanta,GA30328-5571Summerville,SC29483-9665www.tensar-international.comTNS Advanced Technologies By Crown ResourcesVantage Partners, LLC856SPleasantburgDr1000BucksIndustrialParkDrGreenville,SC29607-2455Statesville,NC28625-2575ww.vp-geos.com*List is from theGeosynthetics Materials Association.1.3LOADANDRESISTANCEFACTORDESIGN(LRFD)The most significant revision/update of this reference manual is the change of designprocedure for MSE walls from an allowable stress design (ASD)basis toload and resistancefactor design (LRFD) basis.Transportation superstructures are designed using LRFDprocedures, and logically the substructures supporting the superstructures should also bedesigned on a LRFD basis to provide design consistency on the overall project. Therefore,FHWA and the AASHTO Subcommittee onBridgesand Substructures established anOctober1,2010deadlineforimplementationof LRFDinwalldesign.Although the implementation of LRFDrequires a change in design proceduresfor engineersaccustomed to ASD, many advantages do exist.LRFD separately accounts for uncertainty inboth resistance and load, and when appropriately calibrated, can provide more consistentlevels of safety in the design of superstructure and substructure components in terms ofreliability index.Section 11 of the AASHTO LRFD Specification (2007) providesinformation on LRFD for earth retaining structures including mechanically stabilized earth(MSE) walls. Section 10.4 of AASHTO (2007) provides detailed information on theevaluation of soil and rock properties to be used for design.Section3 of AASHTO (2007)provides detailed information on vertical and lateral loads, and load factors for the design ofretaining walls.For many years, engineers have designed walls for highway and other applications usingallowable stress design (ASD) methods. (Note that the AASHTO (2002) and FHWA (Eliaset al., 2001) ASD references will not be updated by AASHTO or FHWA, respectively.) InFHWA NHI-10-0241-Introduction112MSEWalls andRSS-VolINovember2009
Strata Systems, Inc., Div. Glen Raven, Inc. PO Box 791 Statesville, NC 28687-0791 www.geogrid.com SynTeen Technical Fabrics 1950 W Meeting St Lancaster, SC 29720-8811 www.synteen.com Tenax Corp. 4800 E Monument St Baltimore, MD 21205-3031 TenCate Geosynthetics 365 S Holland Dr Pendergrass, GA 30567-4625 www.tencate.com Tensar International Corporation 5883 Glenridge Dr NE Ste 200 Atlanta, GA 30328-5571 www.tensar-international.com Thrace-LINQ Inc. 2550 W 5th North St Summerville, SC 29483-9665 TNS Advanced Technologies By Crown Resources 856 S Pleasantburg Dr Greenville, SC 29607-2455 Vantage Partners, LLC 1000 Bucks Industrial Park Dr Statesville, NC 28625-2575 www.vp-geos.com * List is from the Geosynthetics Materials Association. 1.3 LOAD AND RESISTANCE FACTOR DESIGN (LRFD) The most significant revision/update of this reference manual is the change of design procedure for MSE walls from an allowable stress design (ASD) basis to load and resistance factor design (LRFD) basis. Transportation superstructures are designed using LRFD procedures, and logically the substructures supporting the superstructures should also be designed on a LRFD basis to provide design consistency on the overall project. Therefore, FHWA and the AASHTO Subcommittee on Bridges and Substructures established an October 1, 2010 deadline for implementation of LRFD in wall design. Although the implementation of LRFD requires a change in design procedures for engineers accustomed to ASD, many advantages do exist. LRFD separately accounts for uncertainty in both resistance and load, and when appropriately calibrated, can provide more consistent levels of safety in the design of superstructure and substructure components in terms of reliability index. Section 11 of the AASHTO LRFD Specification (2007) provides information on LRFD for earth retaining structures including mechanically stabilized earth (MSE) walls. Section 10.4 of AASHTO (2007) provides detailed information on the evaluation of soil and rock properties to be used for design. Section 3 of AASHTO (2007) provides detailed information on vertical and lateral loads, and load factors for the design of retaining walls. For many years, engineers have designed walls for highway and other applications using allowable stress design (ASD) methods. (Note that the AASHTO (2002) and FHWA (Elias et al., 2001) ASD references will not be updated by AASHTO or FHWA, respectively.) In FHWA NHI-10-024 1 – Introduction MSE Walls and RSS – Vol I 1 – 12 November 2009
ASD, all uncertainty in applied loads and material resistance are combined in a factor ofsafety or allowable material stress.Furthermore, the factor of safety is independent of themethod usedto estimate the resistance.InLRFD,uncertaintyin load and material resistanceare accounted for separately.The uncertainty in load is represented by a load factor and theuncertainty in material resistance is represented by a resistance factor. More importantly, theresistance factor is a function of the method used to estimate the resistance and thus themodel uncertainty is also included in the design process.In the AASHTO-LRFD framework, there are four limit states, which represent distinctstructural performance criteria: (1) strength limit states; (2) serviceability limit states, (3)extreme event limit states, and (4) fatigue limit states.For most earth retaining systemdesigns, the strength or service limit states control the design. For walls subject toearthquake or vessel/vehicle impact, the extreme limit states may control.This manual, and the accompanying training course curriculum materials, have beenprepared assuming that the user is familiar with LRFD general procedures Agencies canreceive detailed training and reference materials on LRFD procedures for substructures fromthe FHWA NHI 130082 training course (see www.nhi.fhwa.dot.gov).This manual also provides detailed procedures for the design, specification, and constructionof reinforced soil slopes (RSS). The AASHTO LRFD Bridge Design Specifications (2007)do not address RsS structures.Therefore, the design for RsS remains based upon a limitequilibrium slope stability basis within this manual.FHWA NHI-10-0241-Introduction1-13MSEWallsandRSS-VolINovember2009
ASD, all uncertainty in applied loads and material resistance are combined in a factor of safety or allowable material stress. Furthermore, the factor of safety is independent of the method used to estimate the resistance. In LRFD, uncertainty in load and material resistance are accounted for separately. The uncertainty in load is represented by a load factor and the uncertainty in material resistance is represented by a resistance factor. More importantly, the resistance factor is a function of the method used to estimate the resistance and thus the model uncertainty is also included in the design process. In the AASHTO-LRFD framework, there are four limit states, which represent distinct structural performance criteria: (1) strength limit states; (2) serviceability limit states; (3) extreme event limit states; and (4) fatigue limit states. For most earth retaining system designs, the strength or service limit states control the design. For walls subject to earthquake or vessel/vehicle impact, the extreme limit states may control. This manual, and the accompanying training course curriculum materials, have been prepared assuming that the user is familiar with LRFD general procedures Agencies can receive detailed training and reference materials on LRFD procedures for substructures from the FHWA NHI 130082 training course (see www.nhi.fhwa.dot.gov). This manual also provides detailed procedures for the design, specification, and construction of reinforced soil slopes (RSS). The AASHTO LRFD Bridge Design Specifications (2007) do not address RSS structures. Therefore, the design for RSS remains based upon a limit equilibrium slope stability basis within this manual. FHWA NHI-10-024 1 – Introduction MSE Walls and RSS – Vol I 1 – 13 November 2009
FHWANHI-10-0241-Introduction1 14MSE Walls and RSS-VolINovember2009
FHWA NHI-10-024 1 – Introduction MSE Walls and RSS – Vol I 1 – 14 November 2009
CHAPTER2SYSTEMSANDPROJECTEVALUATIONThis chapter describes available MSE wall (MSEW) and RSS systems and components, theirapplication,advantages,disadvantages andrelative costs.Subsequently,it reviews typicalconstruction sequence for MSEW and RSS construction, and outlines required site andproject evaluations leading to the establishment of site-specific project criteria and details.2.1APPLICATIONS2.1.1MSE WallsMSEW structures are cost-effective alternatives for most applications where reinforcedconcrete or gravity type walls have traditionally been used to retain soil.These includebridge abutments and wing walls, as well as areas where the right-of-way is restricted, suchthat an embankment or excavation with stable side slopes cannot be constructed. They areparticularly suited to economical construction in steep-sided terrain, in ground subject toslope instability,or in areas where foundation soils are poor.MSE walls offer significant technical and cost advantages over conventional reinforcedconcrete retaining structures at sites with poor foundation conditions.In such cases, theelimination of costs for foundation improvements such as piles and pile caps, that may berequired for support of conventional structures, have resulted in cost savings of greater than50percentoncompletedprojects.Representative uses of MSE walls for various applications are shown in Figure 2-1.Temporary MSE wall structures have been especially cost-effective for temporary detoursnecessaryfor highway reconstruction projects. Temporary MSEwalls are used to supporttemporary roadway embankments and temporary bridge abutments,as illustrated in Figure2-2. MSE walls are also used as temporary support of permanent roadway embankments forphased construction, an example is shown in Figure 2-3.FHWA NHI-10-0242-Systems and Project Evaluation2-1MSEWallsandRSS-VolINovember2009
CHAPTER 2 SYSTEMS AND PROJECT EVALUATION This chapter describes available MSE wall (MSEW) and RSS systems and components, their application, advantages, disadvantages and relative costs. Subsequently, it reviews typical construction sequence for MSEW and RSS construction, and outlines required site and project evaluations leading to the establishment of site-specific project criteria and details. 2.1 APPLICATIONS 2.1.1 MSE Walls MSEW structures are cost-effective alternatives for most applications where reinforced concrete or gravity type walls have traditionally been used to retain soil. These include bridge abutments and wing walls, as well as areas where the right-of-way is restricted, such that an embankment or excavation with stable side slopes cannot be constructed. They are particularly suited to economical construction in steep-sided terrain, in ground subject to slope instability, or in areas where foundation soils are poor. MSE walls offer significant technical and cost advantages over conventional reinforced concrete retaining structures at sites with poor foundation conditions. In such cases, the elimination of costs for foundation improvements such as piles and pile caps, that may be required for support of conventional structures, have resulted in cost savings of greater than 50 percent on completed projects. Representative uses of MSE walls for various applications are shown in Figure 2-1. Temporary MSE wall structures have been especially cost-effective for temporary detours necessary for highway reconstruction projects. Temporary MSE walls are used to support temporary roadway embankments and temporary bridge abutments, as illustrated in Figure 2 2. MSE walls are also used as temporary support of permanent roadway embankments for phased construction, an example is shown in Figure 2-3. FHWA NHI-10-024 2 – Systems and Project Evaluation MSE Walls and RSS – Vol I 2 – 1 November 2009