the way forward
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THE WAY FORWARD
or
WHO SAID RESEARCH WAS EASY ?
Relationship between variablesRelationship between variables
x
Y = (say) roughness after 5 years
Poor
Good
Expectation for acceptable performance
Relationship between variablesRelationship between variables
x
Y = (say) roughness after 5 years
Poor
Good
Relationship between variablesRelationship between variables
x
Y = (say) roughness after 5 years
Poor
Good
Relationship between variablesRelationship between variables
x
Y = (say) roughness after 5 years
Poor
Good
Multi-value problemMulti-value problem
Plasticity Index
Y = (say) roughness after 5 years
Poor
Good
Multi-value problemMulti-value problem
Plasticity Index
Y = (say) roughness after 5 years
Poor
Good
Multi-value problemMulti-value problem
Plasticity Index
Y = (say) roughness after 5 years
Very dry
Very wet
Poor
Good
High traffic (conventional)High traffic (conventional)
traffic leveltraffic level subgrade strengthsubgrade strength base typebase type base layer thicknessbase layer thickness base layer strength (for some types)base layer strength (for some types) sub-base layer thicknesssub-base layer thickness sub-base typesub-base type surface layer thicknesssurface layer thickness surface typesurface type climateclimate
33
33
33
33
22
33
22
33
33
33
26,24426,244
THE ROAD DESIGN OR “RISK” ENVIRONMENTTHE ROAD DESIGN OR “RISK” ENVIRONMENT
PREVAILING CLIMATERainfall (intensity, distribution)Temperature (evaporation & diurnal change)Future change or unpredictability
DRAINAGE AND HYDROLOGYGround & surface water flowHydro-genesisDemand of terrainModifying influences
AVAILABLE MATERIALSAlternative & thin bituminous surfacingsPavement materials
•Marginal materials•Standards
•Subgrade & road formation•Problem soils•Moisture sensitivity•Stabilisation options and treatments
GEOMETRICS AND CROSS-SECTION PROFILESRoad widthCrown heightDemand of terrainSealed shoulders
TRAFFIC CHARACTERISTICSAxle loadingTyre pressuresSeasonalityPositionGrowth projections
OTHERTechnology solution
•labour based•Intermediate equip
•Safety•Institutional environment capacity•Financing•Political pressure•Design period•Road side activity
MAINTENANCECapacity & skillsFundingProgramming
CONSTRUCTIONQuality controlCapacity, training & experienceSelection and use of plantInfluence of construction traffic
CONSTRAINTS OF THE “GREEN” ENVIRONMENTConstrained alignmentsAccess to materialsDepletion of resourcesTerrain stability
OPTIMUM OR APPROPRIATE
PAVEMENT DESIGN
METHODOLOGY
Pass/fail criteriaPass/fail criteria
Strength of material
Specification for trunk road
Number ofsamples
Low traffic Low traffic traffic leveltraffic level subgrade strengthsubgrade strength base typebase type base layer thicknessbase layer thickness base layer strength (for all types)base layer strength (for all types) sub-base layer thicknesssub-base layer thickness sub-base typesub-base type surface layer thicknesssurface layer thickness surface typesurface type climateclimate technologytechnology maintenancemaintenance cross section and geometrycross section and geometry drainage drainage ++++
33
33
66
33
33
33
33
33
44
33
22
22
44
33
2 million at least2 million at least
BASIS FOR THE ORN31 BASIS FOR THE ORN31 DESIGNSDESIGNS
Full scale design and performance Full scale design and performance experiments carried out by TRL in experiments carried out by TRL in tropical countriestropical countries
Full scale design and performance Full scale design and performance experiments carried out by others in experiments carried out by others in tropical countriestropical countries
Performance studies of as-built networksPerformance studies of as-built networks Empirically based performance modelsEmpirically based performance models
(eg Highway Design Model III )(eg Highway Design Model III ) Theoretical / mechanistic analysisTheoretical / mechanistic analysis
X
How do we cope ?How do we cope ?
Engineering judgementEngineering judgement
Engineering judgementEngineering judgement
we cannot do without itwe cannot do without it but it is all too easy to draw but it is all too easy to draw
incorrect conclusions so...incorrect conclusions so... one man’s judgement is not one man’s judgement is not
enoughenough we need to know about we need to know about
variability and reliabilityvariability and reliability to do so we need lots of data to do so we need lots of data
WEIGHTED EQUIVALENT ESA APPLICATIONS
103 104 105 106 107 108
EQUIVALENT THICKNESS De, INCHES45
40
35
30
25
20
10
5
0
15
xx
x
xxx x x
xxxxxx
xx
x x xx
xxx
x
x
xx
x
xx x x
xx
xxx xx
x
xx
x
x
AASHO "DESIGN" EQUATION COMPARED WITH DATA
Engineering judgementEngineering judgement
we cannot do without itwe cannot do without it it is all too easy to draw incorrect it is all too easy to draw incorrect
conclusions so...conclusions so... one man’s judgement is not enoughone man’s judgement is not enough to evaluate risk we need lots of data to evaluate risk we need lots of data
consensus necessary - an expert systemconsensus necessary - an expert systemhence this projecthence this project
The way forwardThe way forward
As the projects proceeds there will be As the projects proceeds there will be many issues to be addressedmany issues to be addressed
this meeting has been the ‘literature this meeting has been the ‘literature review’ (as it were)review’ (as it were)
the projects are clearly very ambitious the projects are clearly very ambitious and there is a danger of failing to focus and there is a danger of failing to focus sufficiently on the most important issues sufficiently on the most important issues
we now need to begin to synthesize our we now need to begin to synthesize our experiences to help inform the data experiences to help inform the data collection phasecollection phase
A few observationsA few observations
Variability and improving Variability and improving technologytechnology
do not knock beltsdo not knock belts andand bracesbraces specifications can get tighter and specifications can get tighter and
better as contractors improvebetter as contractors improve there are usually several ways to there are usually several ways to
solve a problem solve a problem it may be unnecessary to agonise it may be unnecessary to agonise
over which is best - they may be over which is best - they may be equally (or almost equally) cost equally (or almost equally) cost effectiveeffective
on the other hand they may not !!!on the other hand they may not !!! so don’t waste money (John Hine)so don’t waste money (John Hine)
And eventually we will need to And eventually we will need to decide how to present the final decide how to present the final
outputoutput
Catalogue of structures?Catalogue of structures? GraphsGraphs ?? Think about itThink about it
The end for nowThe end for now
Consideration of the Road Design Environment for LVSR’s
OPTIMUM OR APPROPRIATE
PAVEMENT DESIGN
PREVAILINGCLIMATE
PREVAILINGCLIMATE
AVAILABLE MATERIALSAVAILABLE MATERIALS
TRAFFIC CHARACTERISTICSTRAFFIC CHARACTERISTICS
CONSTRUCTIONCONSTRUCTION
CONSTRAINTS OF THE “GREEN”
ENVIRONMENT
CONSTRAINTS OF THE “GREEN”
ENVIRONMENT
MAINTENANCEMAINTENANCE
OTHERSOTHERS
GEOMETRICS AND
CROSS-SECTION PROFILES
GEOMETRICS AND
CROSS-SECTION PROFILES
DRAINAGE AND HYDROLOGYDRAINAGE AND HYDROLOGY
DRAINAGE AND HYDROLOGYDRAINAGE AND HYDROLOGY
Ground waterGround water Surface waterSurface water Drainage designDrainage design Permeability of pavement layersPermeability of pavement layers Surface infiltrationSurface infiltration Hydro-genesisHydro-genesis
CLIMATECLIMATE
Rainfall (intensity, distribution)Rainfall (intensity, distribution) Temperature (evaporation & diurnal Temperature (evaporation & diurnal
change)change)
CONSTRUCTIONCONSTRUCTION
Technology and selection and use of Technology and selection and use of plantplant
Quality control and realistic variabilityQuality control and realistic variability Influence of construction traffic (intensity, Influence of construction traffic (intensity,
distribution)distribution)
MAINTENANCEMAINTENANCE
Capacity and skillsCapacity and skills FundingFunding Programming (likely timing)Programming (likely timing)
MATERIALSMATERIALS
Alternative & thin bituminous surfacings Alternative & thin bituminous surfacings Pavement materialsPavement materials
Marginal materialsMarginal materials StandardsStandards
Subgrade & road formationSubgrade & road formation Problem soilsProblem soils Moisture sensitivityMoisture sensitivity Stabilisation options and treatmentsStabilisation options and treatments
GEOMETRICS AND GEOMETRICS AND CROSS-SECTION PROFILES CROSS-SECTION PROFILES
Road widthRoad width Sealed shoulders or notSealed shoulders or not Embankment heightEmbankment height CamberCamber
TRAFFICTRAFFIC
Axle loadingAxle loading Tyre pressuresTyre pressures SeasonalitySeasonality Position on carriagewayPosition on carriageway Vehicle typesVehicle types NMTNMT Growth Growth
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