pavement design flexible pavement
Click here to load reader
-
Upload
an-nur-kamarudin -
Category
Documents
-
view
392 -
download
69
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