ufc_3_250_01_2016.pdf

UFC 3-250-01

14 November, 2016

UNIFIED FACILITIES CRITERIA (UFC)

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

PAVEMENT DESIGN FOR ROADS

AND PARKING AREAS

PAVEMENT DESIGN FOR ROADS AND PARKING AREAS

Any copyrighted material included in this UFC is identified at its point of use.

Use of the copyrighted material apart from this UFC must have the permission of the copyright holder.

U.S. ARMY CORPS OF ENGINEERS

NAVAL FACILITIES ENGINEERING COMMAND (Preparing Activity)

AIR FORCE CIVIL ENGINEER CENTER

Record of Changes (changes are indicated by \1\ ... /1/)

Change No. Date Location

This UFC supersedes UFC 3-250-01FA, dated January, 2004 and UFC 3-230-06A dated January 2004.

FOREWORD

The Unified Facilities Criteria (UFC) system is prescribed by MIL-STD 3007 and provides planning, design, construction, sustainment, restoration, and modernization criteria, and applies to the Military Departments, the Defense Agencies, and the DoD Field Activities in accordance with USD (AT&L) Memorandum dated 29 May 2002. UFC will be used for all DoD projects and work for other customers where appropriate. All construction outside of the United States is also governed by Status of Forces Agreements (SOFA), Host Nation Funded Construction Agreements (HNFA), and in some instances, Bilateral Infrastructure Agreements (BIA.)

Therefore, the acquisition team must ensure compliance with the most stringent of the UFC, the SOFA, the HNFA, and the BIA, as applicable.

UFC are living documents and will be periodically reviewed, updated, and made available to users as part of the Services’ responsibility for providing technical criteria for military construction. Headquarters, U.S. Army Corps of Engineers (HQUSACE), Naval Facilities Engineering Command (NAVFAC), and Air Force Civil Engineer Center (AFCEC) are responsible for administration of the UFC system. Defense agencies should contact the preparing service for document interpretation and improvements. Technical content of UFC is the responsibility of the cognizant DoD working group. Recommended changes with supporting rationale should be sent to the respective service proponent office by the following electronic form: Criteria Change Request. The form is also accessible from the Internet sites listed below.

UFC are effective upon issuance and are distributed only in electronic media from the following source:

• Whole Building Design Guide web site http://dod.wbdg.org/.

Refer to UFC 1-200-01, DoD Building Code (General Building Requirements), for implementation of new issuances on projects.

AUTHORIZED BY:

GEORGE O. LEA, P.E. JOSEPH E. GOTT, P.E.

Chief, Military Engineering Branch Chief Engineer U.S. Army Corps of Engineers Naval Facilities Engineering Command

EDWIN H. OSHIBA, SES, DAF MICHAEL McANDREW Deputy Director of Civil Engineers Director, Facilities Investment and Management DCS/Logistics, Engineering & Office of the Deputy Under Secretary of Defense Force Protection (Installations and Environment) http://www.wbdg.org/pdfs/ufc_implementation.pdf http://www.wbdg.org/ccb/browse_cat.php?o=29&c=4 http://dod.wbdg.org/

REVISION SUMMARY SHEET

Document: UFC 3-250-01, PAVEMENT DESIGN FOR ROADS AND PARKING

AREAS

Superseding: This UFC supersedes UFC 3-250-01FA, dated January, 2004 and UFC 3-230-06A dated January 2004.

Description: This revision provides pavement design procedures and requirements for the pavement design of roads and parking areas worldwide. It clarifies when State pavement design procedures may be used and when Pavement-Transportation Computer Assisted Structural Engineering (PCASE) is required.

Reasons for Document:

• This UFC updates the guidance and requirements for specialized pavement design and underdrain design in two existing criteria documents and efficiently consolidates them into a single UFC.

• Provides consistency in applying pavement design requirements for projects with standard vehicle types, particularly with regard to using State pavement design procedures.

Impact:

This unification effort will result in less cost to maintain DoD criteria and a more efficient pavement design in the following ways:

• By relying on State pavement design procedures for standard vehicle types that typically travel local roads.

• Reduction in the number of references used for military construction provides a clear and efficient guidance for the design and construction of DoD pavements.

• Reduction in ambiguity and the need for interpretation reduces the potential for design and construction conflicts.

Unification Issues:

None.

i

TABLE OF CONTENTS

CHAPTER 1 INTRODUCTION

1-1 PURPOSE AND SCOPE

1-2 APPLICABILITY

1-3 GENERAL BUILDING REQUIREMENTS

1-4 REFERENCES

1-5 GLOSSARY

CHAPTER 2 PRELIMINARY SOIL INVESTIGATION

2-1 GENERAL

2-2 INVESTIGATION OF SITE

2-2.1 Preliminary Site Analysis of Subgrade Conditions

2-2.2 Subsurface Explorations

2-2.3 Dynamic Cone Penetrometer

2-2.4 Soil Classification

2-2.5 Soil Evaluation

2-3 BORROW AREAS

CHAPTER 3 TECHNICAL REQUIREMENTS

3-1 SELECTION OF PAVEMENT TYPE

3-2 DESIGN VARIABLES

3-3 RIGID PAVEMENTS

3-4 FLEXIBLE PAVEMENTS

3-5 MANDATORY USE OF PCASE

3-5.1 Pavement-Transportation Computer Assisted Structural Engineering. .. 6

3-6 MATERIALS

3-7 DRAINAGE SYSTEMS

CHAPTER 4 PAVEMENT DESIGN

4-1 EFFECT OF VEHICULAR TRAFFIC ON PAVEMENT DESIGN

4-2 EQUIVALENT SINGLE AXLE LOAD (ESAL)

4-3 PAVEMENT DESIGN

4-3.1 Vehicle Wander Width

4-3.2 Location of Critical Loads

4-3.3 Mixed Traffic

CHAPTER 5 FLEXIBLE PAVEMENT SUBGRADES

ii

5-1 FACTORS TO BE CONSIDERED

5-2 COMPACTION

5-3 COMPACTION EXAMPLES

5-4 SELECTION OF DESIGN CBR VALUES

CHAPTER 6 FLEXIBLE PAVEMENT SELECT MATERIALS AND SUBBASE

COURSES

6-1 GENERAL

6-2 MATERIALS

6-2.1 Select Materials

6-2.2 Subbase Materials

6-3 COMPACTION

6-4 DRAINAGE

6-5 SELECTION OF DESIGN CBR VALUES

CHAPTER 7 FLEXIBLE PAVEMENT BASE COURSES

7-1 MATERIALS

7-2 COMPACTION

7-3 DRAINAGE

7-4 SELECTION OF DESIGN CBR

7-5 MINIMUM THICKNESS

CHAPTER 8 BITUMINOUS PAVEMENT

8-1 GENERAL

8-2 CRITERIA FOR BITUMINOUS PAVEMENTS

8-3 MINIMUM THICKNESS

CHAPTER 9 FLEXIBLE PAVEMENT DESIGN

9-1 GENERAL

9-2 DESIGN PROCEDURE

9-2.1 Conventional Flexible Pavements

9-2.2 Stabilized Soil Layers

9-2.3 All-Bituminous Concrete

9-3 DESIGN TRAFFIC

9-4 THICKNESS CRITERIA FOR CONVENTIONAL FLEXIBLE

PAVEMENTS

9-5 THICKNESS CRITERIA-STABILIZED SOIL LAYERS

9-5.1 Equivalency Factors iii

9-5.2 Minimum Thickness

9-6 EXAMPLE THICKNESS DESIGN-STABILIZED SOIL LAYERS

9-7 SHOULDERS AND SIMILAR AREAS

9-8 BITUMINOUS SIDEWALKS, CURBS, AND GUTTERS

9-9 FLEXIBLE OVERLAY DESIGN

9-10 FLEXIBLE PAVEMENT DESIGN CURVES

CHAPTER 10 RIGID PAVEMENT DESIGN

10-1 SOIL CLASSIFICATION AND TESTS

10-2 COMPACTION

10-2.1 General

10-2.2 Requirements

10-2.3 Special Soils

10-3 TREATMENT OF UNSUITABLE SOILS

10-4 DETERMINATION OF MODULUS OF SUBGRADE REACTION

CHAPTER 11 RIGID PAVEMENT BASE COURSES

11-1 GENERAL REQUIREMENTS

11-2 MATERIALS

11-3 COMPACTION

11-4 FROST REQUIREMENTS

CHAPTER 12 CONCRETE PAVEMENT

12-1 MIX PROPORTIONING AND CONTROL

12-2 TESTING

12-3 SPECIAL CONDITIONS

CHAPTER 13 PLAIN CONCRETE PAVEMENT DESIGN

13-1 GENERAL

13-2 ROLLER-COMPACTED CONCRETE PAVEMENTS

13-3 DESIGN PROCEDURE

13-4 DESIGN PROCEDURE FOR STABILIZED FOUNDATIONS

13-5 DESIGN EXAMPLES

13-6 CONCRETE SIDEWALKS, CURBS AND GUTTERS

13-7 RIGID PAVEMENT DESIGN CURVES

CHAPTER 14 REINFORCED CONCRETE PAVEMENTS

14-1 APPLICATION

iv

14-1.1 Subgrade Conditions

14-1.2 Economic Considerations

14-1.3 Plain Concrete Pavements

14-1.4 Other Uses

14-2 DESIGN PROCEDURE

14-2.1 Thickness Design on Unbound Base or Subbase

14-2.2 Thickness Design on Stabilized Base or Subgrade

14-3 LIMITATIONS

14-4 DESIGN EXAMPLE

14-5 TYPICAL DETAILS

CHAPTER 15 PAVEMENT OVERLAYS

15-1 GENERAL

15-2 PREPARATION OF EXISTING PAVEMENT

15-2.1 Rigid Overlay

15-2.2 Flexible Overlay

15-3 CONDITION OF EXISTING RIGID PAVEMENT

15-3.1 General

15-3.2 Plain Concrete Overlay

15-3.3 Flexible Overlay

15-4 RIGID OVERLAY OF EXISTING RIGID PAVEMENT

15-4.1 General

15-4.2 Plain Concrete Overlay

15-4.3 Reinforced Concrete Overlay

15-5 RIGID OVERLAY OF EXISTING FLEXIBLE OR COMPOSITE

PAVEMENTS

15-5.1 Flexible Pavements

15-5.2 Composite Base Pavements

15-6 FLEXIBLE OVERLAY OF FLEXIBLE PAVEMENT

15-7 FLEXIBLE OVERLAY OF RIGID BASE PAVEMENT

15-7.1 Design Procedure

15-7.2 Thickness Determination

15-7.3 Jointing

15-8 USE OF GEOTEXTILES TO RETARD REFLECTIVE CRACKING

15-9 OVERLAYS IN FROST REGIONS

v

15-10 OVERLAY DESIGN EXAMPLE

CHAPTER 16 JOINTS FOR PLAIN CONCRETE

16-1 ROADWAYS

16-2 JOINT TYPES AND USAGE

16-2.1 Contraction Joints

16-2.2 Construction Joints

16-2.3 Expansion Joints

16-3 DOWELS

16-4 SPECIAL PROVISIONS FOR SLIP FORM PAVING

16-4.1 Header

16-4.2 Transition Between Different Joints

16-4.3 Transition Between Two Keyed Joints

16-5 JOINT SEALING

16-6 SPECIAL JOINTS AND JUNCTURES

16-6.1 Slip-Type Joints

16-6.2 Joints Between New and Existing Pavements

CHAPTER 17 JOINTS FOR REINFORCED CONCRETE

17-1 REQUIREMENTS

17-1.1 Unscheduled Joints

17-1.2 Thickened-Edge-Type Joints

17-1.3 Transverse Construction Joint

17-1.4 Transverse Contraction Joints

17-1.5 Two Traffic Lanes

17-1.6 Pavement Center Line

17-2 JOINT SEALING

CHAPTER 18 ROLLER-COMPACTED CONCRETE PAVEMENTS

18-1 INTRODUCTION

18-2 LOAD TRANSFER

18-3 THICKNESS DESIGN

18-4 MULTILIFT PAVEMENTS

18-4.1 Full Bond

18-4.2 Partial Bond

18-4.3 No Bond vi

18-5 JOINT TYPES FOR RCCP

18-5.1 Expansion Joints

18-5.2 Contraction Joints

18-5.3 Construction Joints

CHAPTER 19 SEASONAL FROST CONDITIONS

19-1 GENERAL

19-2 FROST-SUSCEPTIBILITY CLASSIFICATION

19-2.1 S1 and S2 Groups

19-2.2 F1 and F2 Groups

19-2.3 Varved Clays

19-2.4 Special Conditions

19-3 ALTERNATIVE METHODS OF THICKNESS DESIGN

19-3.1 Limited Subgrade Frost Penetration Method

19-3.2 Reduced Subgrade Strength Method

19-4 SELECTION OF DESIGN METHOD

19-5 LIMITED SUBGRADE FROST PENETRATION

19-5.1 Air Freezing Index

19-5.2 Design Freezing Index

19-5.3 Design Method

19-5.4 Thickness

19-5.5 Controlling Thickness

19-5.6 Effects of Non-frost Susceptible Criteria

19-6 REDUCED SUBGRADE STRENGTH

19-6.1 Thickness of Flexible Pavements

19-6.2 Thickness of Rigid Pavements

19-7 FREE-DRAINING MATERIAL DIRECTLY BENEATH BOUND BASE OR

SURFACING LAYER

19-8 SOIL STABILIZATION

19-8.1 Bound Base

19-8.2 Stabilization with Lime

19-8.3 Stabilization with Portland Cement

19-8.4 Stabilization with Bitumen

19-9 SUBGRADE REQUIREMENTS

19-9.1 Exception Conditions vii

19-9.2 Treatment of Wet Fine-Grained Subgrades

19-9.3 Cobbles or Boulders

19-9.4 Changes in Soil Conditions

19-9.5 Wet Areas

19-9.6 Rock Excavation

19-9.7 Rock Subgrades

19-10 OTHER MEASURES TO REDUCE HEAVE

19-11 PAVEMENT CRACKING ASSOCIATED WITH FROST HEAVE

19-12 COMPACTION

19-13 USE OF INSULATION MATERIALS IN PAVEMENTS

19-14 DESIGN EXAMPLE HEAVILY TRAFFICKED ROAD

19-15 ALTERNATIVE DESIGNS

CHAPTER 20 DESIGN OF SUBSURFACE PAVEMENT DRAINAGE SYSTEMS

20-1 GENERAL

20-1.1 Effects of Water on Pavements and Subgrade

20-1.2 Traffic Effects

20-1.3 Sources of Water

20-1.4 Classification of Subdrain Facilities

20-1.5 Subsurface Drainage Requirements

20-1.6 Laboratory Tests

20-1.7 Drainage of Water from Soil

20-2 PRINCIPLES OF PAVEMENT DRAINAGE

20-2.1 Flow of Water Through Soils

20-2.2 Factors Affecting Permeability

20-2.3 Quantity and Rate of Subsurface Flow

20-2.4 Use of Drainage Layers

20-2.5 Use of Filters

20-2.6 Use of Separation Layers

20-2.7 Use of Geotextiles

20-3 DESIGN OF THE PAVEMENT SUBSURFACE DRAINAGE SYSTEM. 102

20-3.1 General

20-3.2 Methods

20-3.3 Design Prerequisites viii

20-3.4 Criteria for Subsurface Drain Systems

20-3.5 Placement of Subsurface Drainage System

20-3.6 Material Properties for Drainage Layers

20-4 STABILIZATION OF DRAINAGE LAYER

20-4.1 Choke Stone Stabilization

20-4.2 Asphalt Stabilization

20-4.3 Cement Stabilization

20-5 COLLECTOR DRAINS

20-5.1 Design Flow

20-5.2 Design of Collector Drains

20-5.3 Placement of the Drainage Layer and Collector Drains

20-5.4 Lateral Outlet Pipe

20-5.5 Cross Drains

20-5.6 Manholes and Observation

CHAPTER 21 DESIGN OF AGGREGATE SURFACES

21-1 GENERAL

21-2 ENTRANCES, EXITS, AND SEGMENTS

21-3 THICKNESS CRITERIA (NON-FROST AREAS)

21-4 FROST AREA CONSIDERATIONS

21-4.1 Required Thickness

21-4.2 Required Layers in Pavement Section

21-4.3 Wearing Surface

21-4.4 Base Course

21-4.5 Subbase

21-4.6 Compaction

21-4.7 Thickness of Base Course and Filter Layer

21-4.8 Alternate Design

21-5 SURFACE COURSE REQUIREMENTS

21-5.1 Non-Frost Areas

21-5.2 Frost Areas

21-6 COMPACTION REQUIREMENTS

21-7 DRAINAGE REQUIREMENTS

21-7.1 Materials ix

21-8 DESIGN EXAMPLES

APPENDIX A REFERENCES

APPENDIX B BEST PRACTICES

B-1 CONSTRUCTION OF THE DRAINAGE LAYER

B-1.1 Experience

B-1.2 Placement of Drainage Layer

B-1.3 Compaction

B-1.4 Protection after Compaction

B-1.5 Proof Rolling

B-2 CONSTRUCTION: SEASONAL FROST CONDITIONS

B-2.1 CONTROL OF SUBGRADE AND BASE COURSE CONSTRUCTION.

B-2.2 BASE COURSE CONSTRUCTION

B-2.3 Gradation of Base Course Materials

B-2.4 Visual Inspection

B-3 MAINTENANCE OF SUBSURFACE DRAINAGE SYSTEMS

B-3.1 Monitoring Program

B-3.2 Maintenance Guidelines

B-4 AGGREGATE ROADS

B-4.1 MAINTENANCE REQUIREMENTS

B-4.2 DUST CONTROL

APPENDIX C GLOSSARY

C-1 ACRONYMS

C-2 DEFINITION OF TERMS

C-3 TRI-SERVICE PAVEMENT DETAILS

C-4 UNIFIED SOIL CLASSIFICATION SYSTEM SOIL TYPES

C-5 UNITS OF MEASUREMENT AND UNIT CONVERSIONS

APPENDIX D USE OF INSULATION MATERIALS IN PAVEMENTS

D-1 INSULATING MATERIALS AND INSULATED PAVEMENT SYSTEMS.

D-1.1 Synthetic Insulating Material

D-1.2 Insulated Pavement System

D-2 DETERMINATION OF THICKNESS OF COVER ABOVE INSULATION.

x

D-3 DESIGN OF INSULATED PAVEMENT TO PREVENT SUBGRADE

FREEZING

D-4 DESIGN OF INSULATED PAVEMENT FOR LIMITED SUB GRADE

FREEZING

D-5 CONSTRUCTION PRACTICE

APPENDIX E FLEXIBLE PAVEMENT DESIGN CURVES

APPENDIX F RIGID PAVEMENT DESIGN CURVES

APPENDIX G EXAMPLES

G-1 MIXED TRAFFIC CALCULATION

G-2 COMPACTION REQUIREMENTS

G-2.1 Example 1: Cohesionless Subgrade

G-2.2 Example 2: Cohesive Subgrade

G-3 THICKNESS DESIGN FOR CONVENTIONAL FLEXIBLE PAVEMENTS.

G-3.1 Total Thickness

G-3.2 Minimum Base and Pavement Thicknesses

G-3.3 Thickness of Subbase and Base Courses

G-4 THICKNESS DESIGN FOR STABILIZED SOIL LAYERS

G-4.1 Example 1

G-4.2 Example 2

G-5 THICKNESS DESIGN FOR RIGID PAVEMENTS

G-5.1 Example 1: Non-Stabilized

G-5.2 Example 2: Stabilized Soil

G-6 REINFORCED CONCRETE PAVEMENTS

G-7 OVERLAY DESIGN

G-7.1 Bonded Overlay

G-7.2 Partially Bonded Overlay

G-7.3 Un-bonded Overlay

G-7.4 Flexible Overlay

G-8 DESIGN FOR SEASONAL FROST CONDITIONS

G-8.1 Site and Traffic Characteristics

G-8.2 Subgrade Material

G-8.3 Base Course Material

G-8.4 Subbase Course Material xi

G-8.5 Average Dry Unit Weight

G-8.6 Average Water Content after Drainage

G-8.7 Highest Groundwater

G-8.8 Concrete Flexural Strength

G-8.9 Flexible Pavement Design by Limited Subgrade Frost Penetration Method

G-8.10 Flexible Pavement Design by Reduced Subgrade Strength Method. 267

G-8.11 Rigid Pavement Design by Limited Subgrade Frost Penetration Method.

G-8.12 Rigid Pavement Design by the Reduced Subgrade Strength Method.

G-9 DESIGN OF AGGREGATE SURFACED ROADS

G-9.1 Example 1: Non-Frost Design

G-9.2 Example 2: Frost Design

APPENDIX H DETERMINATION OF FLEXURAL STRENGTH AND MODULUS OF

ELASTICITY

H-1 FLEXURAL STRENGTH TEST PROCEDURE

H-1.1 CALCULATIONS

H-1.2 REPORT

H-2 MODULUS OF ELASTICITY TEST PROCEDURE

xii

FIGURES

Figure 10-1 Effect of Base Course Thickness on Modulus of Soil Reaction for Non-frost

Conditions Figure 14-1 Reinforced Rigid Pavement Design Figure 15-1 Factor for Projecting Cracking in a Flexible Pavement Figure 15-2 Location Guide for the Use of Geotextiles in Retarding Reflective Cracking

Figure 19-1 Determination of Freezing Index Figure 19-2 Distribution of Design Freezing Indexes in North America Figure 19-3 Distribution of Mean Freezing Indexes in Northern Eurasia Figure 19-4A Frost Penetration Beneath Pavements Figure 19-4B Frost Penetration Beneath Pavements Figure 19-4C Frost Penetration Beneath Pavements Figure 19-5 Design Depth of Non-frost Susceptible Base for Limited Subgrade Frost

Penetration Figure 19-6 Frost-Area Index of Reaction for Design of Rigid Roads and Parking Areas

Figure 20-1 Design Storm Index (in/hour), 1-hr Rainfall Intensity-Frequency Data for

Continental United States Excluding Alaska Figure 20-2 Permeability Test Data (from Lambe and Whitman, With Permission) Figure 21-1 Aggregate Surfaced Design Chart; 18-kip Axle (8,200-kg) Figure C14-1 Typical Layout of Joints at Intersection Figure C14-3A Reinforced Rigid Pavement with Two Traffic Lanes Figure C14-3B Reinforced Rigid Pavement with Two Traffic Lanes Figure C14-4 Reinforced Rigid Pavement with Traffic and Parking Lanes Figure C14-5A Layout of Joints at the Intersection of Reinforced Rigid Pavement Figure C14-5B Layout of Joints at the Intersection of Reinforced Rigid Pavement Figure C16-1A Plain Concrete Pavements Figure C16-1B Design Details for Plain Concrete Pavements Figure C16-2 Joint Layout for Vehicular Parking Areas Figure C16-3 Contraction Joints for Plain Concrete Pavements Figure C16-4A Construction Joints for Plain Concrete Pavements Figure C16-4B Construction Joints for Plain Concrete Pavements Figure C16-4C Construction Joints for Plain Concrete Pavements Figure C16-4D Construction Joints for Plain Concrete Pavements Figure C16-5 Expansion Joints for Plain Concrete Pavements Figure C16-6 Thickened-Edge Slip Joint Figure C16-7A Joint Sealants Figure C16-7B Joint Sealants Figure C16-7C Joint Sealants Figure C17-1 Contraction Joints for Reinforced Concrete Pavements Figure C17-2A Construction Joints for Reinforced Concrete Pavements Figure C17-2B Construction Joints for Reinforced Concrete Pavements Figure C17-2C Construction Joints for Reinforced Concrete Pavements Figure C17-2D Construction Joints for Reinforced Concrete Pavements Figure C17-3 Expansions Joints for Reinforced Concrete Pavements Figure C19-7 Tapered Transition Figure C20-1 Collector Drain xiii

Figure C20-2 Collector Drain to Intercept Seepage and Lower the Groundwater Table

Figure C20-3 Pavement Geometry for Computation of Time for Drainage Figure C20-6 Plan View of Subsurface Drainage System Figure C20-7A Typical Interior Subdrain for Rigid Pavement (Non-Frost Areas) Figure C20-7B Typical Interior Subdrain for Rigid Pavement (Frost Areas, Depth of

Frost > Depth to Pipe) Figure C20-7C Typical Interior Subdrain for Rigid Pavement (Frost Areas, Depth of

Frost < Depth to Pipe) Figure C20-8A Typical Edge Subdrain for Rigid Pavement with Shoulder (Non-Frost

Areas) Figure C20-8B Typical Edge Subdrain for Rigid Pavement (Frost Areas) Figure C20-9A Typical Interior Subdrain for Flexible Pavement (Non-Frost Areas) Figure C20-9B Typical Interior Subdrain for Flexible Pavement (Frost Areas, Depth of

Frost > Depth of Pipe) Figure C20-9C Typical Interior Subdrain for Flexible Pavement (Frost Areas, Depth of

Frost < Depth of Pipe) Figure C20-10A Typical Edge Subdrain for Flexible Pavement (Non-Frost Areas) Figure C20-10B Typical Edge Subdrain for Flexible Pavement (Frost Areas) Figure C20-11 Dual Outlet System Layout Figure C20-12 Illustration of Large-Radius Bends Recommended for Drainage Outlet

Figure E-1 Single Axle, Dual-Tire Load Flexible Pavement Design Curve Figure E-2 Passenger Car Flexible Pavement Design Curve Figure E-3 Light Strike Vehicle Flexible Pavement Design Curve Figure E-4 M1A1 Main Tank Flexible Pavement Design Curve Figure E-5 M1A2 Main Tank Flexible Pavement Design Curve Figure E-6 M2A3 Bradley Vehicle Tracked Flexible Pavement Design Curve Figure E-7 M35A2 2.5-Ton Cargo Truck 6x6 Flexible Pavement Design Curve Figure E-8 M60A3 Main Tank Flexible Pavement Design Curve Figure E-9 M109A6, 155 Howitzer Tracked Flexible Pavement Design Curve Figure E-10 M113A1 Armored Carrier Tracked Flexible Pavement Design Curve Figure E-11 M923 5-Ton Cargo Truck 6x6 Flexible Pavement Design Curve Figure E-12 M977 Hemtt 10-Ton Cargo Truck 8x8 Flexible Pavement Design Curve 203 Figure E-13 M978 Hemtt 10-Ton Fuel Truck 8x8 Flexible Pavement Design Curve ... 204 Figure E-14 M983 Hemtt With XM860A1 Trailer Flexible Pavement Design Curve ... 204 Figure E-15 M998 HMMWV 1.25-Ton Carrier Flexible Pavement Design Curve Figure E-16 M988B RTCH FORKLIFT Flexible Pavement Design Curve Figure E-17 M1070 HET Tractor W/M1000 TRL W/M1A1 Tank Flexible Pavement

Design Curve Figure E-18 M1074 Load System w/Crane w/M1076 Trailer Flexible Pavement Design

Curve Figure E-19 M1075 Load System Flexible Pavement Design Curve Figure E-20 M1075 Load System w/M1076 Trailer Flexible Pavement Design Curve 210 Figure E-21 M1078 2.5-Ton Cargo Truck 4x4 Flexible Pavement Design Curve Figure E-22 P-23 Crash Truck (Fire Truck) Flexible Pavement Design Curve xiv

Figure E-23 R-11 Refueler Flexible Pavement Design Curve Figure E-24 Truck, Small Pickup, or SUV Flexible Pavement Design Curve Figure E-25 Truck, Large Pickup, or SUV Flexible Pavement Design Curve Figure E-26 Truck 3-Axle Flexible Pavement Design Curve Figure E-28 Truck 5-Axle Flexible Pavement Design Curve Figure E-29 Truck 2-Axle, 6-Tire Flexible Pavement Design Curve Figure E-30 TYC-850L Container Truck Flexible Pavement Design Curve Figure E-31 75BFMII Mobile Crane Flexible Pavement Design Curve Figure F-1 Single Axle, Dual Tire Load Plain Concrete and RCCP Figure F-2 Passenger Car Plain Concrete and RCCP Figure F-3 Light Strike Vehicle Plain Concrete and RCCP Figure F-4 M1A1 Main Tank Tracked Plain Concrete and RCCP Figure F-5 M1A2 Main Tank Tracked Plain Concrete and RCCP Figure F-6 M2A3, Bradley Vehicle Tracked Plain Concrete and RCCP Figure F-7 M35A2 2.5 Ton Cargo Truck 6x6 Plain Concrete and RCCP Figure F-8 M60A3 Main Tank Tracked Plain Concrete and RCCP Figure F-9 M109A6, 155 Howitzer Tracked Plain Concrete and RCCP Figure F-10 M113A1, Armored Carrier Tracked Plain Concrete and RCCP Figure F-11 M923 5-Ton Cargo Truck Plain Concrete and RCCP Figure F-12 M977 HEMTT, 10-Ton Cargo Truck 8x8 Plain Concrete and RCCP Figure F-13 M978 HEMTT, 10-Ton Fuel Truck 8x8 Plain Concrete and RCCP Figure F-14 M983 HEMTT, w/XM860A1 Trailer Plain Concrete and RCCP Figure F-15 M998 HMMWV, 1.25-Ton Carrier 4x4 Plain Concrete and RCCP Figure F-16 M988B RTCH Forklift Plain Concrete and RCCP Figure F-17 M1070 HET Tractor w/ M1000 TRL W/M1A1 Tank Plain Concrete and

RCCP

Figure F-18 M1074 Load System with Crane Plain Concrete and RCCP Figure F-19 M1075 Load System Plain Concrete and RCCP Figure F-20 M1075 Load System w/M1076 Trailer Plain Concrete and RCCP Figure F-21 M1078 2-1/2 Ton Cargo Truck 4x4 Plain Concrete and RCCP Figure F-21 P-22 Crash Truck (Fire Truck) Plain Concrete and RCCP Figure F-23 R-11 Refueler Plain Concrete and RCCP Figure F-24 Small Pickup Plain Concrete and RCCP Figure F-25 Larger Pickup Plain Concrete and RCCP Figure F-26 Truck 3-Axle Plain Concrete and RCCP Figure F-27 Truck 4-Axle Plain Concrete and RCCP Figure F-28 Truck 5 –Axle Plain Concrete and RCCP Figure F-29 Truck 2-Axle, 6-Tire Plain Concrete and RCCP Figure F-30 TYC-850L Container Truck Plain Concrete and RCCP Figure F-31 75 BFMII Mobile Crane Plain Concrete and RCCP xv

TABLES

Table 4-1 Representative Subgrade Categories Table 5-1 Depth of Compaction for Select Materials and Subgrades (CBR1 ≤ 20) Table 6-1 Maximum Permissible Design Values for Subbases and Select Materials Table 7-1 Design CBR Values Table 7-2 Minimum Thickness of Flexible Pavement Sections Table 9-1 Equivalency Factors for Stabilized Material Table 10-1 Modulus of Soil Reaction (psi/in)* Table 16-1 Allowable Spacing of Longitudinal and Transverse Contraction Joints Table 16-2 Dowel Size and Spacing for Construction, Contraction, and Expansion

Joints Table 19-1 Modes of Distress in Pavements Table 19-2 Frost Design Soil Classification* Table 19-3 Frost-Area Soil Support Indexes for Subgrade Soils for Flexible Pavement

Design Table 20-1 Coefficient of Permeability for Sand and Gravel Materials (Coefficient of 55)

Table 20-2 Frost Susceptible Soils Table 20-3 Gradations of Materials for Drainage Layers and Choke Stone Table 20-4 Properties of Materials for Drainage Layers Table 20-5 Material Gradations for Drainage Layers Table 20-6 Criteria for Granular Separation Layer Table 20-7 Criteria for Filter Fabric to be Used as a Separation Layer Table 20-8 Coefficient of Roughness for Different Types of Pipe Table 20-9 Criteria for Fabrics Used in Trench Construction Table 21 1 Gradation for Aggregate Surface Courses Table 21-2 Compaction Depth Requirements for Aggregate Surfaces Table G-1 Example of Mixed Traffic Calculations for a Flexible Pavement Table G-2 Example of Mixed Traffic Calculations with the 5-axle Truck as Controlling

Vehicle Table G-3 Mixed Traffic with M1A2 Tank, 63,049 kg (139,000 lb) as Controlling Vehicle

Non-Stabilized Foundation Table G-4 Mixed Traffic with M1A2, 63,049 kg (139,000 lb) as Controlling Vehicle

Stabilized Foundation xvi

This Page Intentionally Left Blank

CHAPTER 1 INTRODUCTION

1-1 PURPOSE AND SCOPE.

This UFC provides minimum criteria for the design procedures and requirements for the pavement design of roads and parking areas. It clarifies when State pavement design procedures may be used and when Pavement-Transportation Computer Assisted Structural Engineering (PCASE) is required. Pavement design engineers must use this minimum criteria when making decisions and determining an acceptable pavement design procedure.

1-2 APPLICABILITY.

This UFC applies to all military service elements and contractors involved in the planning, design, and construction of DoD facilities worldwide.

1-3 GENERAL BUILDING REQUIREMENTS.

Comply with UFC 1-200-01, DoD Building Code (General Building Requirements). UFC 1-200-01 provides applicability of model building codes and government unique criteria for typical design disciplines and building systems, as well as for accessibility, antiterrorism, security, high performance and sustainability requirements, and safety.

Use this UFC in addition to UFC 1-200-01 and the UFCs and government criteria referenced therein.

1-4 REFERENCES.

Appendix A contains a list of references used in this document. The publication date of the code or standard is not included in this document. In general, the latest available issuance of the reference is used.

1-5 GLOSSARY.

Appendix C contains acronyms, Unified Soil Classification System (USCS) soil types, units of measure, definition of terms and referenced figures.

CHAPTER 2 PRELIMINARY SOIL INVESTIGATION

2-1 GENERAL.

Soil subgrades provide a foundation for supporting pavements. The strength and uniformity of the subgrade will affect the required pavement thickness and the performance of the pavement during its design life. Conduct a thorough investigation of the subgrade to determine soil characteristics. Soil uniformity and moisture conditions under the pavement are especially important with respect to frost action.

2-2 INVESTIGATION OF SITE.

Characteristics of subgrade soils must be known to predict pavement performance.

Determine the general suitability of the subgrade soils based on classification of the soil, moisture-density relationship, degree to which the soil can be compacted, expansion characteristics, susceptibility to pumping, and susceptibility to detrimental frost action.

Factors such as groundwater, surface infiltration, soil capillarity, topography, rainfall, and drainage conditions will also affect the future support rendered by the subgrade by increasing its moisture content and thereby reducing its strength.

2-2.1 Preliminary Site Analysis of Subgrade Conditions.

Before planning field explorations, conduct a general survey of the topographic and subsurface soil conditions at the site. Investigate previous performance of existing pavements, minimum of five years, on similar local subgrades to assist in evaluating subsurface conditions. Sources of data should include the landforms, soil conditions in ditches, and cuts and tests of representative soils in the site. Augment the survey with existing soil and geological maps. Sources of information include earlier subsurface investigations near the site, United States Geological Survey maps, and soil survey maps. Evaluate surface drainage at the site and subsurface drainage of the subgrade.

2-2.2 Subsurface Explorations.

Conduct subsurface explorations to test each type of soil identified in the preliminary site analysis. Test pits and soil borings may be used for subsurface investigations. The spacing of subsurface explorations along roadways depends on the variability of the existing soil conditions. When preliminary site analysis substantiates soil uniformity, use a maximum spacing of 400 ft (120 m). Make additional subsurface explorations when the preliminary site analysis indicates unusual or potentially troublesome subgrade conditions. When subsurface explorations have previously been conducted to the required depth and those subsurface explorations confirm soil uniformity, the spacing may be increased to a maximum of 1500 ft (450 m) as long as the subsurface explorations results continue to confirm soil uniformity.

The depth of subsurface explorations must extend beyond the frost penetration depth as determined from Chapter titled Seasonal Frost Conditions and be no less than 6 ft (2

m) below finished grade. Depth requirements stated above are measured from the pavement surface.

2-2.3 Dynamic Cone Penetrometer.

The Dynamic Cone Penetrometer (DCP) test can be used to determine design California Bearing Ratio (CBR) values. When using the DCP to determine CBR values in shallow pavement applications, perform test in accordance with ASTM D6951/D6951M.

2-2.4 Soil Classification.

Classify soil samples from the subsurface explorations according to the USCS in ASTM D2487.

2-2.5 Soil Evaluation

Use the subsurface exploration samples to compute soil properties, prepare soil profiles and to select soils for further testing. To help identify soft layers in the soil, evaluations must include moisture content.

2-3 BORROW AREAS.

Perform preliminary subsurface explorations in areas where material is to be borrowed from adjacent areas. Extend subsurface explorations to a minimum depth of 2 to 4 ft (0.6 to 1.2 m) below the anticipated depth of borrow. Use the preliminary samples to classify soils, compute moisture content, and determine compaction characteristics.

CHAPTER 3 TECHNICAL REQUIREMENTS

3-1 SELECTION OF PAVEMENT TYPE.

Use rigid pavements or composite pavements with a rigid overlay for the following areas:

• Vehicle Maintenance Areas.

• Pavements for All Vehicles with Non-pneumatic Tires.

• Open Storage Areas with Materials Having Non-pneumatic Loadings in Excess of 200 psi (1.38 MPa), covered or uncovered.

• Hardstands (Organizational Vehicle Parking Areas, Motor Pool, Unit’s Equipment Parking).

• Pavements Supporting Tracked Vehicles.

• Vehicle Wash Racks.

• Vehicle Fueling Pads.

Exception: For architectural or special operational requirements design pavements based upon life-cycle cost analysis.

3-2 DESIGN VARIABLES.

The prime factor influencing the structural design of a pavement is the required load-carrying capacity. The thickness of pavement necessary to provide the desired load-carrying capacity is a function of the following variables:

• Vehicle gross loads and wheel configurations.

• Volume of traffic during the design life of pavement.

• Soil strength.

• Modulus of rupture (flexural strength).

3-3 RIGID PAVEMENTS.

The rigid pavement design procedures presented in this UFC are based upon the critical tensile stresses produced within the pavement by the vehicle loading.

Correlation between theory, small-scale model studies, and full-scale accelerated traffic tests show that maximum tensile stresses in the pavement occur when the vehicle wheels are tangent to a free or unsupported edge of the pavement. Stresses for the condition of the vehicle wheels tangent to a longitudinal or transverse joint are less severe because of the use of load-transfer devices and aggregate interlock in these joints to transfer a portion of the load across the joint. Because of their cyclic nature, other stresses are, at times, additive to the vehicle load stresses. These other stresses include restraint stresses resulting from thermal expansion and contraction of the pavement and warping stresses resulting from moisture and temperature gradients within the pavement. Provision for those stresses not induced by wheel loads is included in design factors developed empirically from full-scale accelerated traffic tests and from the observed performance of pavements under actual service conditions.

3-4 FLEXIBLE PAVEMENTS.

The design procedure used by DoD to design flexible pavements for roads and parking areas is referred to as the Beta Criteria design procedure. This procedure requires that each layer be thick enough to distribute the stresses induced by traffic so that when such stresses reach the underlying layer they will not overstress the underlying layer causing excessive shear deformation. The Beta Criteria is used to sketch the design curves contained in Appendix E. Besides the determination of layer thicknesses, adequately compact each layer so that traffic does not induce excessive settlement.

Use ASTM D1557 compaction effort procedures to design against consolidation under traffic.

3-5 MANDATORY USE OF PCASE.

PCASE is mandatory for the design of roads and parking areas trafficked by special military vehicles and for all vehicle types outside of the United States and its territories and possessions. Refer to UFC 3-201-01 for the types of vehicles characterized as special military vehicles.

PCASE is also mandatory for the design of organizational vehicle parking areas.

3-5.1 Pavement-Transportation Computer Assisted Structural Engineering.

PCASE is a computer program developed by the United States Army Corps of Engineers (USACE), Engineer Research and Development Center (ERDC), is available for use by the public. PCASE can be used to determine pavement thickness and compaction requirements. The computer program runs on the Microsoft Windows™ operating systems or Windows™ compatible systems. PCASE may be obtained electronically from the following:

• https://transportation.wes.army.mil/pcase or http://www.pcase.com

• A compact disk (CD) is also available from the U.S. Army Corps of Engineers, Transportation Systems Center, 1616 Capitol Avenue, Omaha, NE 68102-4901.

3-6 MATERIALS.

Materials for pavements designed in accordance with this UFC and PCASE must conform to requirements set forth in this and the Unified Facility Guide Specifications (UFGS). To the greatest practical extent, specify local materials that meet requirements of the Department of Transportation in the State in which the project is located, and are in accordance to UFC requirements. Only the materials should be changed in the UFGS, all other requirements such as general requirements, tolerances, and execution requirements should stay the same. The construction materials for pavements designed using state Department of Transportation (DoT) thickness design criteria must https://transportation.wes.army.mil/pcase http://www.pcase.com/ conform to the DoT material specifications. The construction execution procedure for physically determining acceptable conditions, preparation, installation, field quality control and inspection must conform to the UFGS.

3-7 DRAINAGE SYSTEMS.

Pavement subdrainage systems are covered in this UFC. Refer to UFC 3-201-01 for criteria on storm drainage systems (e.g. surface drainage, underground drainage systems, stormwater management facilities, erosion and sediment control). Refer to UFC 3-210-01 for criteria on low impact development.

CHAPTER 4 PAVEMENT DESIGN

For the design of pavements traveled by standard American Association of State Highway and Transportation Officials (AASHTO) vehicles or vehicles not characterized as special military vehicles in UFC 3-201-01, in the United States, the State pavement design procedure may be used, except that the use of keyed joint, if allowed by the State, must not be used on pavement thinner than 9 inches. When using the State pavement design procedure, use the pavement design criteria and procedures recognized by the Department of Transportation (DoT) in the state in which the project is located. Refer to UFC 3-201-01, paragraph titled “Design Traffic” to predict average daily traffic (ADT) when using a State pavement design procedure.

4-1 EFFECT OF VEHICULAR TRAFFIC ON PAVEMENT DESIGN.

Design pavement thickness to withstand the anticipated traffic, categorized by type and weight of vehicles, and number of passes of each type for the design life of the pavement. For most pavements, the magnitude of the axle load is of greater importance than the gross weight of pneumatic-tired vehicles because axle spacing is generally so large that there is little interaction between the wheel loads of one axle and the wheel loads of the other axles. Thus, for the case of pneumatic-tired vehicles having equal axle loads, the increased severity of loading imposed by conventional four or five axle trucks as compared with that imposed by two or three axle trucks is largely a fatigue effect resulting from an increased number of load repetitions per vehicle operation. For forklift trucks where the loading is concentrated largely on a single axle and for tracked vehicles where the loading is evenly divided between the two tracks, the severity of the vehicle loading is a function of the gross weight of the vehicle and the frequency of loading. Relations between load repetition and required rigid pavement thickness developed from accelerated traffic tests of full-scale pavements have shown that, for any given vehicle, increasing the gross weight by as little as 10 percent can be equivalent to increasing the volume of traffic by as much as 300 to 400 percent.

Therefore, for rigid pavements, the magnitude of the vehicle loading must be used as a more significant factor in the design of pavements than the number of load repetitions.

4-2 EQUIVALENT SINGLE AXLE LOAD (ESAL).

The ESAL used in this UFC is not the ESAL as computed by the AASHTO Guide for Design of Pavement Structures. In PCASE, the equivalency used is based on mixed traffic and the CBR Beta design model. Direct comparison or equivalence between AASHTO and PCASE ESAL is not straightforward since the ESAL computation in each methodology derives from specific models, assumptions, and design procedures. The conversion of each vehicle to ESALs is based on research done by the USACE, ERDC.

4-3 PAVEMENT DESIGN.

Unless specified otherwise in the project specific requirements, design pavement based upon anticipated vehicles and loadings for a 25 year life; however, sections must not be less than the minimums indicated in UFC 3-201-01. Pavements design is based on loads and the total number of passes during the life of the pavement for the expected vehicles. Typically, traffic is counted in terms of ADT. This ADT value should take into consideration the type, numbers of passes, and load for each of the vehicles in the mix.

The ADT in the daily traffic distribution is converted to total number of passes for the desired pavement design life.

For example, if a road is to be designed for an average of 10 passes per day of a 5 axle truck, then the total design passes for a 25 year life will be 10 passes/day × 365 days/year × 25 years = 91,250 total passes. Design charts have been prepared using PCASE and can be used in lieu of PCASE. These charts are for flexible and rigid pavements use required thickness and total number of passes for various vehicles and are provided in Appendix E, and Appendix F, respectively. When designing for a mix of vehicles (mixed traffic), the concept of an equivalent vehicle is used. In this procedure each vehicle is converted to a critical or controlling vehicle, which in turn represents the cumulative effect of all vehicles in the mix. This procedure is the same procedure used to convert mixed traffic to an equivalent number of passes of an 18,000 lb (8,200 kg) single-axle, dual load ESAL. Use the number of ESALs to compute the minimum pavement layer thicknesses and compaction requirements.

4-3.1 Vehicle Wander Width.

As vehicles travel down a road, there is a natural tendency for the vehicles to wander from side to side. This lateral wander determines the actual number of load or stress repetitions applied to a given point on the pavement. This effect is accounted for in pavement design by the wander width, which is defined as the total width of pavement over which the centerline of a vehicle is distributed 75 percent of the time symmetrically around the mean. Traffic studies have indicated that the wander width for roads is about 33 in (850 mm) assuming a statistical normal distribution of traffic. This means that a vehicle would deviate laterally from its centerline a maximum distance of 165 in (420 mm) from its line of travel. The pavement design charts presented in this UFC are based on these assumptions.

4-3.2 Location of Critical Loads.

In roads with 12 ft (4 m) wide lanes, the location where the maximum loads are applied is about 0 to 3 ft (0 to 1 m) from the pavement edge. If no mechanisms are provided to transfer tire load to the adjacent shoulders, a condition of zero load transfer occurs at the pavement edge. This has a marked impact on the stresses that a concrete slab will be subjected to. In rigid pavements, the Westergaard theoretical analysis for edge stresses is used to compute these critical stresses and no reduction due to load transfer is performed. In flexible pavements, the concept of cumulative damage associated with each vehicle is used to account for the lateral wander and vertical stress applied to the subgrade.

4-3.3 Mixed Traffic.

The examples included in Appendix G illustrate the procedure for handling mixed traffic for either flexible or rigid pavements. The mixed traffic procedure performs an equivalency between vehicles by calculating the thickness requirements of each vehicle for the specified number of passes and subgrade CBR. The vehicle with the largest required thickness then becomes the controlling vehicle and the other vehicles converted to it by the procedure described in the examples. The calculations are based on the thickness requirements of each individual vehicle; therefore the resulting controlling vehicle for flexible and rigid pavements may be different. Since subgrade conditions may vary along a road, mixed traffic calculations use a representative subgrade strength category instead of a specific value. These representative subgrade categories are shown in Table 4-1. However, when the final mixed traffic equivalency has been finished in terms of the equivalent passes of the controlling vehicle, the design CBR or k value will be used to obtain the required pavement thickness above the subgrade.

Table 4-1 Representative Subgrade Categories

Subgrade Category

Flexible Pavements, CBR Range

Representative CBR Value

Rigid Pavements k-value Range psi/in1 Representative k-value, psi/in1

A CBR ≥ 13 15 k ≥ 442 552.6 B 8 < CBR <13 10 221 < k < 442 294.7 C 4 < CBR ≤ 8 6 92 < k ≤ 221 147.4 D CBR ≤ 4 3 k ≤ 92 73.7

1 kPa/mm = psi/in ÷ 0.271

CHAPTER 5 FLEXIBLE PAVEMENT SUBGRADES

5-1 FACTORS TO BE CONSIDERED.

Consider the following primary factors regarding subgrades for flexible pavement design:

• The general characteristics of the subgrade soils (e.g. soil classification, limits).

• Depth to bed rock.

• Depth to groundwater table (including perched groundwater table).

• The attainable compaction in the subgrade and the adequacy of the existing density in the layers below the zone of compaction requirements

• The CBR that the compacted subgrade and un-compacted subgrade will have under local environmental conditions.

• The presence of weak soft layers in the subsoil.

• Susceptibility to detrimental frost action.

• Expansion potential

5-2 COMPACTION.

The natural density of the subgrade must be sufficient to resist densification under traffic or the subgrade must be compacted during construction to a depth where the natural density will resist densification under traffic. Table 5-1 shows the depth, measured from the pavement surface, at which a given percent compaction is required to prevent densification under traffic. Subgrades in cuts must have natural densities equal to or greater than the values shown in Table 5-1. Where such is not the case, compact the subgrade from the surface to meet the tabulated densities, or remove and replace the subgrade, in which case the requirements for fills apply. As another option, cover the subgrade with sufficient selected material, subbase, and base so that the un-compacted subgrade is at a depth where the in place densities are satisfactory. In fill areas, place cohesionless soils at no less than 95 percent of ASTM D1557 maximum density and cohesive fills at less than 90 percent of ASTM D1557 maximum density.

Table 5-1 Depth of Compaction for Select Materials and Subgrades (CBR1 ≤ 20)

Equivalent Passes of an 18,000-lb (8,200-kg) ESAL Depth of Compaction2 or Percent Compaction Shown, in

Type of Pavement Cohesive Soils PI>5; LL>25 Cohesionless Soils PI≤ 5, LL≤

Flexible Rigid 100 95 90 85 80 100 95 90 85 80 < 15,500 < 1,300 3 7 10 14 17 7 13 19 25 33 < 67,500 < 1,500 4 8 12 16 20 8 15 22 29 38 < 295,000 < 34,000 4 9 14 18 23 9 17 25 33 43

< 1.3 million < 343,000 5 11 16 21 26 11 20 28 37 48 < 5.7 million < 2.1 million 6 12 18 23 28 12 22 31 40 53 < 25 million < 9.2 million 7 14 19 25 31 14 24 35 44 58 < 112 million < 37 million 7 15 21 28 34 15 26 38 48 63 < 500 million < 105 million 8 16 23 30 37 16 29 41 52 68

< 2,200 million < 290 million 9 18 25 32 40 18 31 44 56 74 ≥ 2,200 million ≥ 290 millions 10 20 28 35 43 20 34 47 59 77

1 California Bearing Ratio (ASTM D4429).

2 Depth of compaction is measured from pavement surface.

5-3 COMPACTION EXAMPLES.

Appendix G includes two examples illustrating the application of subgrade compaction requirements

5-4 SELECTION OF DESIGN CBR VALUES.

Flexible pavements may be designed using the laboratory soaked CBR, the field in-place CBR, the CBR from the Dynamic Cone Penetrometer as described in ASTM D6951/D6951M or the CBR from undisturbed samples as described in ASTM D1883 or ASTM D 4429. For the design of flexible pavements in areas where no previous experience regarding pavement performance is available, the laboratory soaked CBR is normally used. Where an existing pavement is available at the site that has a subgrade constructed to the same standards as the job being designed, in-place tests or tests on undisturbed samples may be used in selecting the design CBR value. In-place tests are used when the subgrade material is at the maximum water content expected in the prototype and frost is not expected to penetrate the subgrade. Contrarily, tests on undisturbed samples are used where the material is not at the maximum water content and thus soaking is required. Sampling involves considerably more work than in-place tests and undisturbed samples tend to be slightly disturbed. Therefore, in-place tests should be used where possible. Guides for determining when in-place tests can be used are given in details of the CBR test in ASTM D4429.

CHAPTER 6 FLEXIBLE PAVEMENT SELECT MATERIALS AND SUBBASE

COURSES

6-1 GENERAL.

This UFC designates layers between the subgrade and base course as selected materials or subbases. Select materials are those with design CBR values equal to or less than 20; subbases are those with CBR values above 20. Minimum thicknesses of pavement and base have been established to eliminate the need for subbases with design CBR values above 50. Where the design CBR value of the subgrade without processing is in the range of 20 to 50, select materials and subbases may not be needed. However, the subgrade cannot be assigned design CBR values of 20 or higher unless it meets the gradation and plasticity requirements for subbases.

6-2 MATERIALS.

Use the soils investigations described in Chapter titled Preliminary Soils Investigation to determine the location and characteristics of suitable soils for select material and subbase construction.

6-2.1 Select Materials.

The subbase materials for each CBR value must conform to the quality and gradations requirements given in the guide specifications so that they will develop the needed strengths. Select materials are normally locally available coarse-grained soils (gravel:

GW, GP, GM, GC, or sand: SW, SP, SM, SC), although fine-grained soils in the ML and CL groups may be used in certain cases. Consider limerock, coral, shell, ashes, cinders, caliche, disintegrated granite, and other such materials when they are economical. Recommended plasticity requirements are listed in Table 6-1. A maximum aggregate size of 3 in (80 mm) is suggested to aid in meeting grading requirements.

Select material subbases are typically only used with subgrade CBR values less than 4 and large ESAL traffic volumes. Where frost is expected to penetrate the material, the subbase course must also meet the frost criteria in paragraph titled Free-Draining Material Directly Beneath Bound Base Or Surfacing Layer for free-draining material that contain 2.0 percent or less, by weight, of grains that can pass the No. 200 sieve.

6-2.2 Subbase Materials.

Subbase materials may consist of naturally occurring coarse-grained soils or blended and processed soils. Materials such as limerock, coral, shell, ashes, cinders, caliche, and disintegrated granite may be used as subbases when they meet the requirements described in Table 6-1. The existing subgrade may meet the requirements for a subbase course or it may be possible to treat the existing subgrade to produce a subbase. However, use native or processed materials only when the unmixed subgrade meets the liquid limit and plasticity index requirements for subbases. Do not “cut” plasticity by mixing subgrade. Material stabilized with commercial additives may be economical as a subbase. Portland cement, lime, fly ash, or bitumen and combinations thereof are commonly used for this purpose. Also, it may be possible to decrease the plasticity of some materials by use of lime or Portland cement in sufficient amounts to make them suitable as subbases. When using ash or cinders, the free lime content must be less than 5% and the material must be volumetrically stable.

6-3 COMPACTION.

Compaction of subbases will be 100 percent of ASTM D1557 density except where it is known that a higher density can be obtained, in which case the higher density should be required.