TABLEOFCONTENTS-VolumeI1-1CHAPTER1INTRODUCTION1.11-1OBJECTIVES1-11.1.1Scope1-21.1.2SourceDocuments1-31.1.3Terminology1.21-4HISTORICALDEVELOPMENT1.31-12LOADANDRESISTANCEFACTORDESIGN(LRFD)2-1CHAPTER2SYSTEMSANDPROJECTEVALUATION2.12-1APPLICATIONS2-12.1.1 MSEWalls2-42.1.2Reinforced Soil Slopes.2.22-6ADVANTAGESANDPOTENTIALDISADVANTAGES2-62.2.1AdvantagesofMechanicallyStabilizedEarth(MSE)Walls2-62.2.2AdvantagesofReinforcedSoilSlopes(RSS)2-72.2.3Potential Disadvantages2.3.2-7RELATIVE COSTS.2.42-10DESCRIPTIONOFMSE/RSSSYSTEMS2.4.12-10Systems Differentiation2.4.22-11Types of Systems.2.4.32-12Facing Systems.2.4.42-16Reinforcement Types.2.4.52-17Reinforced Fill Materials2.4.62-18AppurtenantMaterialsofConstruction2.52-18CONSTRUCTIONSEQUENCE.2-182.5.1ConstructionofMSEWsystemswithprecastfacings2.5.2.2-24Construction of MSEsystems withFlexibleFacings2.5.3RSS Construction2-282.62-28SITE EVALUATION.2.6.12-28Site Exploration.2.6.22-30Field Reconnaissance...2-302.6.3Subsurface Exploration2.6.42-32Laboratory Testing..2.6.52-33Foundation Soils2.72-34PROJECTEVALUATION.2.7.12-34Structure SelectionFactors2-352.7.2Geologic and TopographicConditions2.7.32-36Environmental Conditions2.7.42-37Size and Nature of Structure.2.7.5.2-38Aesthetics2.7.62-38QuestionableApplications2.82-38ESTABLISHMENTOFPROJECTCRITERIA2-392.8.1Alternates2.8.22-39Facing Considerations...FHWA NHI-10-024Tableof ContentsMSEWallsandRSS-VolINovember2009
TABLE OF CONTENTS – Volume I CHAPTER 1 INTRODUCTION . 1-1 1.1 OBJECTIVES. 1-1 1.1.1 Scope . 1-1 1.1.2 Source Documents . 1-2 1.1.3 Terminology. 1-3 1.2 HISTORICAL DEVELOPMENT . 1-4 1.3 LOAD AND RESISTANCE FACTOR DESIGN (LRFD) . 1-12 CHAPTER 2 SYSTEMS AND PROJECT EVALUATION . 2-1 2.1 APPLICATIONS . 2-1 2.1.1 MSE Walls . 2-1 2.1.2 Reinforced Soil Slopes. 2-4 2.2 ADVANTAGES AND POTENTIAL DISADVANTAGES. 2-6 2.2.1 Advantages of Mechanically Stabilized Earth (MSE) Walls. 2-6 2.2.2 Advantages of Reinforced Soil Slopes (RSS). 2-6 2.2.3 Potential Disadvantages . 2-7 2.3 RELATIVE COSTS. 2-7 2.4 DESCRIPTION OF MSE/RSS SYSTEMS. 2-10 2.4.1 Systems Differentiation . 2-10 2.4.2 Types of Systems . 2-11 2.4.3 Facing Systems . 2-12 2.4.4 Reinforcement Types . 2-16 2.4.5 Reinforced Fill Materials . 2-17 2.4.6 Appurtenant Materials of Construction . 2-18 2.5 CONSTRUCTION SEQUENCE . 2-18 2.5.1 Construction of MSEW systems with precast facings . 2-18 2.5.2 Construction of MSE systems with Flexible Facings . 2-24 2.5.3 RSS Construction. 2-28 2.6 SITE EVALUATION . 2-28 2.6.1 Site Exploration . 2-28 2.6.2 Field Reconnaissance . 2-30 2.6.3 Subsurface Exploration . 2-30 2.6.4 Laboratory Testing . 2-32 2.6.5 Foundation Soils . 2-33 2.7 PROJECT EVALUATION. 2-34 2.7.1 Structure Selection Factors . 2-34 2.7.2 Geologic and Topographic Conditions . 2-35 2.7.3 Environmental Conditions . 2-36 2.7.4 Size and Nature of Structure. 2-37 2.7.5 Aesthetics. 2-38 2.7.6 Questionable Applications . 2-38 2.8 ESTABLISHMENT OF PROJECT CRITERIA . 2-38 2.8.1 Alternates . 2-39 2.8.2 Facing Considerations. 2-39 FHWA NHI-10-024 Table of Contents MSE Walls and RSS – Vol I v November 2009
2.8.312-40PerformanceCriteria.2.8.4DesignLife.2-462.92-46PROPRIETARYASPECTS2.102-47CASEHISTORIES--MSEWALLS.2-472.10.1Mn/DOTCrosstownProject MSEWalls.2-492.10.2VeteransMemorialOverpassTrueAbutmentMSEWalls.2-502.10.3 SEATACRunwayExtension Wall2-512.10.4GuanellaPassRoadwayReconstructionCHAPTER3SOILREINFORCEMENTPRINCIPLES.3-1AND SYSTEMDESIGNPROPERTIES3.1.3-1OVERVIEW3.2ESTABLISHMENTOFENGINEERINGPROPERTIESBASEDONSITE3-2EXPLORATIONANDTESTING3-23.2.11Reinforced Fill Soil..3-83.2.2RetainedBackfill and NaturalRetained Soil3-93.2.3Electrochemical Properties3.3.3-10REINFORCEDSOILCONCEPTS.3-103.3.1StressTransferMechanisms.3.3.23-12Mode of Reinforcement Action3-123.3.3GeometricCharacteristics..3.4SOILREINFORCEMENTINTERACTIONUSINGNORMALIZED3-13CONCEPTS3-133.4.1EvaluationofPulloutPerformance3.4.2Estimate of the Reinforcement Pullout Capacity in MSE Structures ... 3-163-213.4.3Interface Shear.3.53-22ESTABLISHMENTOFSTRUCTURALDESIGNPROPERTIES3-22Strength Properties of Steel Reinforcements3.5.13-283.5.2StrengthPropertiesofGeosyntheticReinforcement.3-313.5.2.a Ultimate Tensile Strength, Tult..3-313.5.2.bInstallationDamageReductionFactor,RFD.3-323.5.2.cCreepReductionFactor,RFcR3-333.5.2.dDurabilityReductionFactor, RF.3-383.5.2.eDurabilityReductionFactor,RFp,atWallFaceUnit3-383.5.2.fLRFDGeosyntheticResistanceFactor,.3-393.5.2.g Preliminary Design Reduction Factor, RF.3-403.5.2.h Serviceability Limit State3.63-41FACING MATERIALS.3-413.6.11PrecastConcretePanels3-413.6.1.a Segmental Panels..3-423.6.1.b Full-Height Panels .3.6.2.3-43ModularBlock Wall (MBW)Units.3-463.6.3Welded Wire Mesh Facing3.6.43-47Geosynthetic Wrap-Around Facing3.6.53-47OtherFacings3.6.6..3-50Two-Stage Facings.FHWA NHI-10-024Table of ContentsviMSEWallsandRSS-VolINovember2009
2.8.3 Performance Criteria . 2-40 2.8.4 Design Life. 2-46 2.9 PROPRIETARY ASPECTS . 2-46 2.10 CASE HISTORIES - MSE WALLS . 2-47 2.10.1 Mn/DOT Crosstown Project MSE Walls. 2-47 2.10.2 Veterans Memorial Overpass True Abutment MSE Walls. 2-49 2.10.3 SEATAC Runway Extension Wall . 2-50 2.10.4 Guanella Pass Roadway Reconstruction. 2-51 CHAPTER 3 SOIL REINFORCEMENT PRINCIPLES AND SYSTEM DESIGN PROPERTIES . 3-1 3.1 OVERVIEW . 3-1 3.2 ESTABLISHMENT OF ENGINEERING PROPERTIES BASED ON SITE EXPLORATION AND TESTING . 3-2 3.2.1 Reinforced Fill Soil . 3-2 3.2.2 Retained Backfill and Natural Retained Soil . 3-8 3.2.3 Electrochemical Properties . 3-9 3.3 REINFORCED SOIL CONCEPTS . 3-10 3.3.1 Stress Transfer Mechanisms . 3-10 3.3.2 Mode of Reinforcement Action . 3-12 3.3.3 Geometric Characteristics . 3-12 3.4 SOIL REINFORCEMENT INTERACTION USING NORMALIZED CONCEPTS . 3-13 3.4.1 Evaluation of Pullout Performance . 3-13 3.4.2 Estimate of the Reinforcement Pullout Capacity in MSE Structures . 3-16 3.4.3 Interface Shear . 3-21 3.5 ESTABLISHMENT OF STRUCTURAL DESIGN PROPERTIES . 3-22 3.5.1 Strength Properties of Steel Reinforcements . 3-22 3.5.2 Strength Properties of Geosynthetic Reinforcement. 3-28 3.5.2.a Ultimate Tensile Strength, Tult . 3-31 3.5.2.b Installation Damage Reduction Factor, RFID . 3-31 3.5.2.c Creep Reduction Factor, RFCR . 3-32 3.5.2.d Durability Reduction Factor, RFD. 3-33 3.5.2.e Durability Reduction Factor, RFD, at Wall Face Unit . 3-38 3.5.2.f LRFD Geosynthetic Resistance Factor, . 3-38 3.5.2.g Preliminary Design Reduction Factor, RF . 3-39 3.5.2.h Serviceability Limit State . 3-40 3.6 FACING MATERIALS . 3-41 3.6.1 Precast Concrete Panels . 3-41 3.6.1.a Segmental Panels . 3-41 3.6.1.b Full-Height Panels . 3-42 3.6.2 Modular Block Wall (MBW) Units . 3-43 3.6.3 Welded Wire Mesh Facing . 3-46 3.6.4 Geosynthetic Wrap-Around Facing . 3-47 3.6.5 Other Facings . 3-47 3.6.6 Two-Stage Facings. 3-50 FHWA NHI-10-024 Table of Contents MSE Walls and RSS – Vol I vi November 2009
4-1CHAPTER4DESIGNOFMSEWALLS4.14-1DESIGNMETHODOLOGYANDANALYSISMETHODS4-14.1.1LoadandResistanceFactorDesign(LRFD)Platform4-24.1.2Analysis Methods..4.2..4-3LOADSANDLOADCOMBINATIONS4.3.4-6DESIGNOFMSEWALLSUSINGLRFDMETHODOLOGY.4-74.3.1Design Steps.4.4MSE WALLS DESIGNGUIDELINES.4-9.4-94.4.1Step1-EstablishProjectRequirements4-94.4.2Step2-Establish Project Parameters4.4.3Step3-EstimateWallEmbedment Depth &Reinforcement Length...4-104.4.4Step 4 - Define Nominal Loads4-114.4.5Step 5 - Summarize Load Combinations, Load Factors, and Resistance4-17Factors.4.4.64-18Step 6- Evaluate External Stability.4-194.4.6.a Evaluate Sliding Stability.4-224.4.6.bEvaluateEccentricity4-264.4.6.cEvaluateBearingonFoundation..4-314.4.6.dSettlementEstimate4.4.7.4-31Step7-EvaluateInternal Stability.4-324.4.7.a Select Type of Reinforcement.4-334.4.7.bDefineCriticalSlipSurface4-354.4.7.cDefine Unfactored Loads4-384.4.7.d Establish Vertical Layout of Soil Reinforcements...4-394.4.7.e CalculateFactored TensileForces in Reinforcements...4-474.4.7.fCalculateSoilReinforcementResistance....4-494.4.7.g Select Grade of &/or Number of Elements at Each Level4-494.4.7.h Internal Stability with Respect to Pullout Failure4-524.4.7.iCheckConnectionStrength..4-574.4.7.j Lateral Movements....4-574.4.7.kVerticalMovementandBearingPads.4-584.4.8Step8-DesignofFacingElements...4-584.4.8.aDesign ofConcrete, Steel, and TimberFacings.4-594.4.8.bDesign of FlexibleWallFacings.4-594.4.9Step9-AssessOverall Stability4-614.4.10 Step 10 - Assess Compound Stability4-654.4.11 Step 11-WallDrainage Systems.4-654.11.aSurfaceDrainage4-654.11.b Surface Water Runoff4.11.cScour4-654.5..4-66TEMPORARYWALLS4.6.4-66DESIGNCHECKLIST..4.7.4-80COMPUTER-AIDEDDESIGN4.8.4-80VENDOR4.94-80STANDARDMSEWDESIGNSFHWA NHI-10-024Tableof ContentsviiMSEWallsandRSS-VolINovember2009
CHAPTER 4 DESIGN OF MSE WALLS . 4-1 4.1 DESIGN METHODOLOGY AND ANALYSIS METHODS . 4-1 4.1.1 Load and Resistance Factor Design (LRFD) Platform . 4-1 4.1.2 Analysis Methods. 4-2 4.2 LOADS AND LOAD COMBINATIONS . 4-3 4.3 DESIGN OF MSE WALLS USING LRFD METHODOLOGY . 4-6 4.3.1 Design Steps. 4-7 4.4 MSE WALLS DESIGN GUIDELINES . 4-9 4.4.1 Step 1 - Establish Project Requirements . 4-9 4.4.2 Step 2 - Establish Project Parameters . 4-9 4.4.3 Step 3 - Estimate Wall Embedment Depth & Reinforcement Length . 4-10 4.4.4 Step 4 - Define Nominal Loads . 4-11 4.4.5 Step 5 - Summarize Load Combinations, Load Factors, and Resistance Factors . 4-17 4.4.6 Step 6 - Evaluate External Stability. 4-18 4.4.6.a Evaluate Sliding Stability . 4-19 4.4.6.b Evaluate Eccentricity . 4-22 4.4.6.c Evaluate Bearing on Foundation. 4-26 4.4.6.d Settlement Estimate . 4-31 4.4.7 Step 7 - Evaluate Internal Stability . 4-31 4.4.7.a Select Type of Reinforcement . 4-32 4.4.7.b Define Critical Slip Surface . 4-33 4.4.7.c Define Unfactored Loads . 4-35 4.4.7.d Establish Vertical Layout of Soil Reinforcements. 4-38 4.4.7.e Calculate Factored Tensile Forces in Reinforcements. 4-39 4.4.7.f Calculate Soil Reinforcement Resistance . 4-47 4.4.7.g Select Grade of &/or Number of Elements at Each Level . 4-49 4.4.7.h Internal Stability with Respect to Pullout Failure. 4-49 4.4.7.i Check Connection Strength . 4-52 4.4.7.j Lateral Movements . 4-57 4.4.7.k Vertical Movement and Bearing Pads . 4-57 4.4.8 Step 8 - Design of Facing Elements. 4-58 4.4.8.a Design of Concrete, Steel, and Timber Facings . 4-58 4.4.8.b Design of Flexible Wall Facings. 4-59 4.4.9 Step 9 - Assess Overall Stability. 4-59 4.4.10 Step 10 - Assess Compound Stability . 4-61 4.4.11 Step 11 - Wall Drainage Systems . 4-65 4.11.a Surface Drainage. 4-65 4.11.b Surface Water Runoff . 4-65 4.11.c Scour . 4-65 4.5 TEMPORARY WALLS . 4-66 4.6 DESIGN CHECKLIST . 4-66 4.7 COMPUTER-AIDED DESIGN . 4-80 4.8 VENDOR. 4-80 4.9 STANDARD MSEW DESIGNS . 4-80 FHWA NHI-10-024 Table of Contents MSE Walls and RSS – Vol I vii November 2009
5-1CHAPTER5MSEWALLDESIGNDETAILS5-15.1TOPOFWALLELEMENTS5-15.1.1Copings.5-45.1.2Traffic Barriers.5-45.1.3Parapets..5-45.1.4Post and Beam Barriers.5-65.1.5DrainageRelated toTopof WallElements5.2BOTTOMOFWALLELEMENTS...5-65.3..5-8DRAINAGE...5-95.3.1Internal Drainage Systems5.3.25-17ExternalDrainage.5-245.3.3Filtration andDrainage SystemComponentRequirements.5.3.45-34Maintenance of Drainage.5.45-35INTERNAL DETAILS...5.4.15-35ContactBetweenDissimilarMetals.5.4.25-35Vertical Obstructions in Reinforced Soil Mass5.4.35-42Horizontal Obstructions inReinforced Soil Mass5-445.4.4Wall Face Penetrations5.4.55-46Slip Joints..5-475.4.6Wall Curves.5-515.4.7Wall Corners.5-525.4.8Two-StageFacing5.55-54WALLINITIATIONS AND TERMINATIONS5.65-56AESTHETICS6-1CHAPTER6DESIGNOFMSEWALLSWITHCOMPLEXGEOMETRICS.6-36.1BRIDGEABUTMENTS6-36.1.1MSEWAbutmentsonSpreadFootings.6.1.2MSEWAbutments on StubFootings SupportedbyDeepFoundations.6-6through Reinforced Wall Fill6.1.36-10Alternative Configuration of MSEWalls at BridgeAbutments6-116.1.4ProtectionofMSEWall atAbutments6.2.6-13SUPERIMPOSED(TIERED)MSEWALLS6-136.2.1 2-Tier Superimposed Wall6-156.2.2SuperimposedWallswithMorethan2-Tiers6.3.6-16WALLSWITHUNEVENREINFORCEMENTLENGTHS6.4.6-17BACK-TO-BACK(BBMSE)WALLS...6.5SHOREDMSEWALLSFORSTEEPTERRAINSANDLOWVOLUME6-19ROADS.6.66-26STABLEFEATURE MSE (SFMSE)WALLS.7-1CHAPTER7DESIGNOFMSEWALLSFOREXTREMEEVENTS.7-17.1SEISMICEVENTS.7-17.1.1 External Stability.7-97.1.2Internal Stability..7-117.1.2.a Tensile Failure7.1.2.b Pullout Failure.7-12FHWA NHI-10-024Table of ContentsviliMSEWallsandRSS-VolINovember2009
CHAPTER 5 MSE WALL DESIGN DETAILS . 5-1 5.1 TOP OF WALL ELEMENTS . 5-1 5.1.1 Copings . 5-1 5.1.2 Traffic Barriers. 5-4 5.1.3 Parapets. 5-4 5.1.4 Post and Beam Barriers. 5-4 5.1.5 Drainage Related to Top of Wall Elements . 5-6 5.2 BOTTOM OF WALL ELEMENTS . 5-6 5.3 DRAINAGE. 5-8 5.3.1 Internal Drainage Systems . 5-9 5.3.2 External Drainage . 5-17 5.3.3 Filtration and Drainage System Component Requirements. 5-24 5.3.4 Maintenance of Drainage. 5-34 5.4 INTERNAL DETAILS . 5-35 5.4.1 Contact Between Dissimilar Metals. 5-35 5.4.2 Vertical Obstructions in Reinforced Soil Mass . 5-35 5.4.3 Horizontal Obstructions in Reinforced Soil Mass . 5-42 5.4.4 Wall Face Penetrations . 5-44 5.4.5 Slip Joints. 5-46 5.4.6 Wall Curves . 5-47 5.4.7 Wall Corners . 5-51 5.4.8 Two-Stage Facing . 5-52 5.5 WALL INITIATIONS AND TERMINATIONS . 5-54 5.6 AESTHETICS. 5-56 CHAPTER 6 DESIGN OF MSE WALLS WITH COMPLEX GEOMETRICS . 6-1 6.1 BRIDGE ABUTMENTS . 6-3 6.1.1 MSEW Abutments on Spread Footings . 6-3 6.1.2 MSEW Abutments on Stub Footings Supported by Deep Foundations through Reinforced Wall Fill . 6-6 6.1.3 Alternative Configuration of MSE Walls at Bridge Abutments . 6-10 6.1.4 Protection of MSE Wall at Abutments . 6-11 6.2 SUPERIMPOSED (TIERED) MSE WALLS. 6-13 6.2.1 2-Tier Superimposed Wall . 6-13 6.2.2 Superimposed Walls with More than 2-Tiers . 6-15 6.3 WALLS WITH UNEVEN REINFORCEMENT LENGTHS . 6-16 6.4 BACK-TO-BACK (BBMSE) WALLS . 6-17 6.5 SHORED MSE WALLS FOR STEEP TERRAINS AND LOW VOLUME ROADS. 6-19 6.6 STABLE FEATURE MSE (SFMSE) WALLS . 6-26 CHAPTER 7 DESIGN OF MSE WALLS FOR EXTREME EVENTS. 7-1 7.1 SEISMIC EVENTS . 7-1 7.1.1 External Stability . 7-1 7.1.2 Internal Stability. 7-9 7.1.2.a Tensile Failure . 7-11 7.1.2.b Pullout Failure. 7-12 FHWA NHI-10-024 Table of Contents MSE Walls and RSS – Vol I viii November 2009
7.1.3 FacingReinforcementConnections7-137.27-14VEHICULARIMPACTEVENTS7-157.2.1Traffic Barriers....7-177.2.2Postand Beam Railings7.37-18FLOODSANDSCOURFHWA NHI-10-024TableofContentsMSE Walls and RSS- VolINovember2009ix
7.1.3 Facing Reinforcement Connections . 7-13 7.2 VEHICULAR IMPACT EVENTS . 7-14 7.2.1 Traffic Barriers. 7-15 7.2.2 Post and Beam Railings . 7-17 7.3 FLOODS AND SCOUR . 7-18 FHWA NHI-10-024 Table of Contents MSE Walls and RSS – Vol I ix November 2009