pavement design flexible pavement

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Transcript of pavement design flexible pavement

  • MAP 1053/SAB 4813

    Pavement Design & Construction/ Advanced Highway Engineering

    Semester 1, 2013/14

    Dr. Haryati Yaacob

  • Office Location

    M50- Room 02-34

    07-5538666/ 019-7341405 [email protected] [email protected]

  • Topic 1 Flexible Pavement Design: AASHTO Method, Asphalt Institute Method, ATJ 5/85 (1985) Road Note 31 - ATJ 5/85 (revised 2013) ( Self Study and Group Assignment)

    Topic 2 Rigid Pavement Design

    - Concrete pavement in Malaysia - Concrete pavement elements - Subgrade and sub-base design - Shoulder options - Design of rigid pavement

    - AASHTO Method - PCA Method

    - Joints - Steel design

    Topic 3 Surface Dressing Topic 4 Interlocking Block Pavement (Self Study and Group Assignment)

  • Recommended Text

    Huang, Y.H., Pavement Analysis and Design, Prentice Hall, 1993.

    Freddy L. Roberts et. Al., Hot Mix Asphalt Materials, Mixture Design and Construction, NAPA, 1996.

    Yoder & Witczak, Principles of Pavement Design, Wiley Publications, 1975.

  • Flexible Pavement

    Structure Surface course

    (waterproof, anti-skid) Base course Subbase course Subgrade

  • Types of Flexible Pavement

    Dense-graded

    Open-graded Gap-graded

  • Pavement types

  • Type of Pavement & their Load Distribution

  • Pavement Types & How They Effect the Subgrade

  • Pavement Design

    Design the pavement thick enough to ensure the strength of the subgrade is not exceeded for the loads to which it will be exposed

  • Pavement Design

    When a pavement is too thin the strength of the subgrade is exceeded and the pavement experiences high strain causing it it to fatigue and eventually fail

  • Pavement Design

    Design the pavement thickness to ensure bending results in STRAIN < 100 (NCHRP 9-38)

  • Structural Design of Flexible Pavements

    Subgrade

    Granular Subbase Layer Granular Base Layer

    Binder Layer

    Surface Layer

  • Design Procedures

    AASHTO Method Asphalt Institute Method ATJ 5/85 Road Note 31 JKR 2006

  • AASHTO METHOD

  • Development of Design

    AASHO Road Test Basis for most currently acceptable design

    methods Importance of traffic loads and repetition

    Design has been largely an empirical

    process Current AASHTO Procedure

  • AASHTO Design Method AASHTO is still a statistically based

    empirical design method Original models revised and extended to

    make them more widely applicable

  • AASHTO Design Variables

    Time Traffic Reliability Materials Environment Serviceability

  • Time

    Performance Period Time from initial

    constrxn to first rehab Time between rehabs

    Analysis Period

    Time that any design must cover

    Often equal to performance period

    Highway Analysis Period

    High Volume Urban 30 - 50

    High-Volume Rural 20 - 50

    Low-volume paved 15 - 25

    Low-volume aggregate surface

    10 - 20

  • 20

    Determining Vehicle Damage Factors (Truck or ESAL Factors)

    Average damaging effect of vehicle

    Consider axle weight distribution for particular vehicle type

    Expresses ESALs/Vehicle

  • 21

    ESALs Equivalent Single Axle Loads

    Used for highway pavements to convert mixed

    traffic to a number of standard axles for design

    Defined as: Total # of applications of a standard axle (generally

    18,000 lb single) required to produce the same damage or loss of serviceability as a number of applications of one or more different axle loads and/or configurations over life of pavement

  • 22

    ESAL Calculation

    ESALi = Current Traffic x Growth Factor x 365 x ESAL Factor

    =

    =m

    iitotal ESALESAL

    1

  • 23

    Growth Rates Large errors can result in ESAL calcs from poor

    estimates of future traffic

    Best estimates are obtained by forecasting vehicle types separately

    Forecasting techniques include Historical trends (regression) Engineering judgment Compound interest equation Straight line projections

  • 24

    Predict Future

    How fast will traffic grow?

    What is the design level of traffic?

    Examine historical trends Develop best estimate of future growth

    rate Apply growth factor to current volume

    ggFactorGrowth

    n 1)1( +=

  • 25

  • 26

    Lane and Directional Distributions Typical Assumptions

    Directional distribution = 50% Lane Distribution

    # Lanes/Direction %Traffic In Design Lane

    1 100

    2 80-100

    3 60-80

    4 or more 50-75

  • 27

    Lane and Directional Distributions

    Typically design for heaviest loaded lane

    Develop best information regarding lane distribution

  • Conversion of mix traffic to ESALs

  • Reliability Definitions

    Reliability = 1 P[Failure]

    The reliability of a pavement design-performance process is the probability that a pavement section designed using the process will perform satisfactorily over the traffic and environmental conditions for the design period.

    1993 AASHTO Guide

  • Variability

    Need design standard deviation Account for variability of all input variables

    Recommended values

    S0 = 0.45 (flexible) S0 = 0.35 (rigid)

  • Reliability Recommended Reliability

    Functional Class Urban Rural

    Interstate/Freeway 85-99.9 80-99.9

    Principle Arterials 80-99 75-95

    Collectors 80-95 75-95

    Local 50-80 50-80

  • Serviceability

  • Materials

    Need to characterize stiffness E, Mr

    Account for seasonal variability

    Determine structural coefficients

  • Environment

    Need to consider freeze/thaw and swelling of soils AASHTO has an established procedure We will not go through the procedure

  • Seasonal Effects on Unbound Layers

    10

    100

    10001-

    Feb

    3-M

    ar

    2-A

    pr

    2-M

    ay

    1-Ju

    n

    1-Ju

    l

    31-J

    ul

    30-A

    ug

    29-S

    ep

    29-O

    ct

    28-N

    ov

    28-D

    ec

    Date

    Elas

    tic M

    odul

    us, M

    Pa

  • Seasonal Effects on HMAC Cell 1 - Mn/ROAD (1993-1996)

    100

    1000

    10000

    100000

    0 30 60 90 120 150 180 210 240 270 300 330 360

    Day of Year

    Mod

    ulus

    , MPa

  • AASHTO Design Values

    Select average values for everything but not subgrade

    Compute relative stiffness of subgrade for design

  • Effective Subgrade Modulus/ Effective Roadbed Soil Resilient Modulus, Mreff

    Definition: an equivalent modulus that would result in the same damage if

    seasonal modulus values were actually used

  • Finding Mreff

    Find seasonal modulus every month Non destructive defection testing

  • Finding Mreff Find relative damage, uf for each season Uses AASHTO Damage Equation

    f = 1.18x108MR-2.32

    Determine weighted average uf Find Mreff corresponding to uf

  • Structural Number

    SN = a1D1 + a2m2D2 + + anmnDn

    Functions of layer thickness, layer coefficients and drainage coefficients

  • Structural Coefficients

    ai = measure of relative ability of a unit thickness of a given material to function as a structural component of the pavement

  • Asphalt Concrete Structural Coefficient , a1

  • Granular Base Layer Coefficient , a2

  • Granular Subbase Layer Coefficient , a3

  • Drainage Coefficient

    Depends on quality of drainage and availability of moisture

    Quality Water < 1% 1 -5 % 5 - 25% > 25% Removed Excellent 2 hours 1.40 - 1.35 1.35 - 1.30 1.30 - 1.20 1.20 Good 1 day 1.35 - 1.25 1.25 - 1.15 1.15 - 1.00 1.00 Fair 1 week 1.25 - 1.15 1.15 - 1.05 1.05 - 0.80 0.80 Poor 1 month 1.15 - 1.05 1.05 - 0.80 0.80 - 0.60 0.60 Very Poor Never Drain 1.05 - 0.95 0.95 - 0.75 0.75 - 0.40 0.40

    mi Values for Modifying Structural Layer Coefficients (Untreated Base and Subbase Materials)

    % Time Saturated 95%

  • Drainage

    Percent time the layer approaches saturation :

    P = % time saturated S = days of spring thaw R = remaining days with rain if pavement will

    drain to 85% in 24 hours, otherwise use days of rain x drainage time in days

    P = (S + R) / 365 * 100

  • Design Equation

    Based on road test Determines number of ESALs before PSI

    is reached

    ( )

    ( )

    07.8log32.2

    110944.0

    5.12.4log

    20.01log36.9log19.5

    018 +

    ++

    +++= RR M

    SN

    PSI

    SNSZW

  • Design Procedure

    Determine SN required above each layer

    Find thickness to satisfy SN above each layer

  • AASHTO Layer Thickness Determination

    Subbase E3 a3 m3 Base E2 a2 m2

    Surface E1 a1 SN3 SN2 SN1

    D1 D2 D3

    Roadbed Soil

    SN= a1D1 + a2D2m2 + a3D3m3

    D1 SN1/a1

    D2 ( SN2- a1D1)/ a2m2

    D3 (SN3- a1D1-a2D2m2)/a3m3

  • Example

    Calculate D1, D2 and D3. Given: E1= 400,000psi; E2= 30, 000psi; E3= 11,000 a1= 0.42; a2=0.14; a3= 0.08 m2=m3=1.3 Mreff = 5,700 psi w18= 18.6 x 106

    R = 95% So= 0.35 PSI = 2.1

  • Example An urban interstate flexible pavement consist of dual carriageway with two

    lanes per direction is to be designed using AASHTO 1993 design guide. The flexible pavement is designed to cater with ESAL value of 7.0 x 106 (both directions) for the next of 20 years. Total relative damage due to 12 months soil seasonal modulus values was recorded as 3.82. The drainage was judged be good and it is estimated that the subbase and base for the pavement structure will be exposed to moisture levels approaching saturation 10 percent of the time. Additional information is given below:

    Resilient modulus of the asphalt concrete at 68F =300 000 psi The granular base CBR = 70% and Mr= 28 000 psi An untreated granular subbase has a CBR =15% and Mr = 12 000 psi Standard deviation = 0.45 Initial serviceability = 4.5 Terminal serviceability = 2.5 Please clearly state all your assumptions. Guidelines are given in Tables

    and Figures below.

  • Asphalt Institute Method

    Mechanistic-Empirical Design

  • Design Criteria Mechanics of materials coupled with

    observed performance

    Number of Loads Until Failure

    Stre

    ss o

    r Stra

    in

  • Performance Equations

    Fatigue 11% AC VTM 5% 20% Cracking at AASHO Road Test

    Rutting

    Rut Need to have good materials, compaction

    854.0291.3

    *10796.0

    = EN

    tf

    477.49 110365.1

    =

    vrN

  • Traffic Analysis

    Use ESALs for detailed analysis Same process as AASHTO

    SN = 5 pt = 2.5

  • Materials

    Resilient modulus and Poissons ratio

    Poissons Ratio Soils = 0.45 Other materials = 0.35

  • Soils modulus determination

    ***Discussion based on handouts give. Determine the design level from modulus

    measurements Charts account for seasonal changes

    Design level function of traffic Build in reliability safety factor

    ESAL Design Value % 1,000,000 87.5

  • Base Materials

    Should meet requirements below

    Test Subbase Base

    CBR, min 20 80

    R-Value, min 55 78

    LL, max 25 25

    PI, max 6 NP

    Sand Eq., min 25 35

    P200 12 7

  • Design charts

    Design charts were developed based Temperature

    3 Regions New York: 45F North Carolina: 60F Arizona: 75F

    Pavement Type Full depth HMA HMA over Emulsified Asphalt Bases- Three types

    I: dense graded aggregate, similar to HMA II: semiprocessed aggregate III: mixes with sands or silty sands

    HMA over untreated aggregate Base HMA and emulsified Asphalt over Untreated Aggregate Base

  • AI Design Procedure

    Select pavement type Select region Determine traffic Determine MR Use design charts to find thickness

  • Example

    MR = 10, 000 psi , ESAL = 106, Determine thickness : Full depth HMA HMA surface over type II emulsified asphalt

    base HMA over 8 untreated aggregate base HMA and emulsified asphalt mix over 8

    untreated aggregate base

  • AI Minimum Thicknesses

    ESALs Min HMA over Type I Min HMA over Type II & Type III

    104 1 2

    105 1.5 2

    106 2 3

    107 2 4

    >107 2 5

  • Total HMA thickness, including both surface and base course

  • Combine thickness of HMA surface course and emulsified asphalt base course. I mixes with processes dense graded agg which should be mixed in a plant and have properties similar to HMA II- mixes with semiprocessed, crusher run, pit run or bank run agg III mixes with sands or silty sand

  • ATJ 5/85 Design Method

  • Data required

    1. Design period proposed 10 years 2. JKR Hierarchy 3. Average Daily Traffic (opening year) - PLH 4. Percentage of Commercial Vehicle - Pc 5. Traffic Growth Rate - r 6. Sub-grade strength - CBR 7. Terrain

  • 1. Estimate Vo = PLH x (1/2) x 365 x (Pc/100) 2. Determine Vc= Vo [(1 + r)n - 1] / r 3. Convert to ESA, ESA = Vc x e ( e = 2.52) Guide for equivalent factor, e

    Design Procedure

  • Design Procedure 4. Check capacity (Table 4.2, 4.3, 4.4- refer

    handouts) 5. Determine Sub-grade CBR In case of varying CBR for 1m depth of sub-grade, mean CBR is

    determined as follows: CBReff = [(h1CBR11/3 + h2CBR21/3 + + hnCBRn1/3) / (1000)]3 where: CBReff = effective CBR CBR1, CBR2, CBRn = CBR of soil strata h1, h2, hn = thickness of soil strata (mm) h1 + h2 + + hn = 1000 mm

  • 6. Design Procedure- Determine TA from nomograph

  • Design Procedure

    7. Calculate thickness for each layer (Table 4.5, 4.6, 4.7, refer handouts)

    TA = SN = a1D1 + a2 D2 + ... + anDn

  • Design Procedure

  • Design Procedure 8. Sketch thickness obtained

  • Design Example

    JKR 05, carriageway width = 7.5m, shoulder = 2.0m ADT = 6600 Pc = 15 % r = 7 % Sub-grade CBR = 5 % Rolling Terrain Material: Surfacing = AC Road base = wet mix Macadam Sub-base = sand

  • Road Note 31

  • Road Note 31

    Designed for tropical and sub-tropical countries to carry up to 30M CSA

    Heavy vehicle > 3 ton Equivalence: e = (L/Ls)4.5

  • Design procedure

    1. Estimate CSA for design life >>> T (Table 4.8, refer handouts)

  • Design procedure 2. Assess sub-grade strength >>> S (Table 4.9, 4.10,

    refer handouts)

  • Design procedure 3. Select combination of material and

    thickness from structure catalogues based on T and S

  • Structure catalogue: Granular road base/surface dressing

  • Structure catalogue: Granular road base/structural surface

  • Design Example

    1. ADT = 250/day.dir, Pc = 55 %, r = 5 %, CBR = 7 %

    2. CSA = 12M, PI > 45, WT = 2m below

    formation

    MAP 1053/SAB 4813Office Location Slide Number 3Recommended TextFlexible PavementTypes of Flexible PavementPavement typesType of Pavement & their Load DistributionPavement Types & How They Effect the SubgradePavement DesignPavement DesignPavement DesignStructural Design of Flexible PavementsDesign ProceduresAASHTO METHODDevelopment of DesignAASHTO Design MethodAASHTO Design VariablesTimeDetermining Vehicle Damage Factors (Truck or ESAL Factors)ESALsESAL CalculationGrowth RatesPredict Future Slide Number 25Lane and Directional DistributionsLane and Directional DistributionsSlide Number 28ReliabilityVariabilityReliabilityServiceabilityMaterialsEnvironmentSeasonal Effects on Unbound LayersSeasonal Effects on HMACAASHTO Design ValuesEffective Subgrade Modulus/ Effective Roadbed Soil Resilient Modulus, Mreff Finding MreffSlide Number 40Finding MreffStructural NumberStructural CoefficientsAsphalt Concrete Structural Coefficient , a1Granular Base Layer Coefficient , a2Granular Subbase Layer Coefficient , a3Drainage CoefficientDrainageDesign EquationSlide Number 50Design ProcedureSlide Number 52AASHTO Layer Thickness DeterminationExampleExampleAsphalt Institute MethodDesign CriteriaPerformance EquationsTraffic AnalysisMaterialsSoils modulus determinationBase MaterialsDesign chartsAI Design ProcedureExampleAI Minimum ThicknessesSlide Number 67Slide Number 68Slide Number 69Slide Number 70Data requiredDesign ProcedureDesign Procedure6.Design Procedure- Determine TA from nomograph Design ProcedureDesign ProcedureDesign ProcedureDesign ExampleRoad Note 31Road Note 31Design procedureDesign procedureDesign procedureStructure catalogue: Granular road base/surface dressingStructure catalogue: Granular road base/structural surfaceDesign Example