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OVERVIEW
1
• Objectives of COURAGE
• Participation in the project
• Work Package Activities
• Key Findings of Technical Work Packages
Work Package 2 - Mechanical Characterisation of UGMs
Work Package 3 - Variability of In-situ Condition
Work Package 4 - Modelling of Pavement Structures
Work Package 5 - Dissemination
COURAGE project aims to:
• extend the understanding of the mechanical behaviour of unbound granular materials used in pavements.
• characterise material behaviour in a manner suitable for application in pavement design for performance prediction (data for mechanistic design, develop appropriate models).
• attempt to validate laboratory data with measured pavement performance data (using lab. test data in computer model of pavement ---> check strains determined from analysis with those measured in field).
• apply knowledge to develop better materials and methods of use.
• findings for European pavement design and maintenance personnel.2
COURAGE OBJECTIVES
The partners and associate partners in COURAGE are:
3ie, 12 participants from 9 EU countries, ECU532,000 (approx. £373,000)
COURAGE PARTICIPANTS
Coordinator
WORK PACKAGE ACTIVITIES
4
The activities of COURAGE:
• WP1 - project management and co-ordination.
• WP2 - laboratory testing with some larger scale testing. simple testing - conventional and unconventional (eg. shape tests and
attrition by gyratory compaction). fundamental testing - more complex (eg. repeated load triaxial). simulative testing (eg. wheel tracking on a small-scale pavement).
• WP3 - collection, comprehension & prediction of in-situ conditions
study in-situ variability in pavements due to climate, topography, etc
The activities of the COURAGE:
• WP4 - material behaviour patterns model and classify materials. conduct full-scale pavement tests (use modelled material lab. test data in
pavement analysis computer models to predict performance - strains).
• WP5 - liaison & dissemination with technical experts outside of the project (e.g. AMADEUS, COST 337) technical evaluation and dissemination of the whole project's work.
5
WORK PACKAGE ACTIVITIES (cont) ….
Aim:• to define tests and “standardise” test procedures for determining key
performance properties of unbound granular materials.• compare the results of these “complex” tests (eg. RLT) with those
of simpler tests (Static TXL test).• assess a number of granular materials, representative of those used
in different European countries. Rank these materials.
Why do we need to know this?• to adopt a systematic approach to determining key properties.• to obtain data for:
material performance comparisons (durability and modulus or strain with conditions ….. density, MC, geology and grading)
interpretation using material models use in full-scale pavement analysis / modelling in WP4
7
Work Package 2
8
In the past anticipated granular material performance has relied heavily upon a product's conformance with standard classification tests, eg:
• Particle Size Distribution (Grading) • Plasticity Limits (PI, LL, Linear Shrinkage)• Los Angeles Value
Perhaps other supplementary tests have also been used:• Washington Degradation• Texas Ball Mill• 10% Fines
Pavement field control tests used, eg. field dry density, moisture content
a number of pavement failures have resulted over the years
Background for WP2
9
However, it is recognised that pavement performance is strongly controlled by the following conditions / factors:
• Stresses generated in the pavement due to traffic loadings• Material state of density, moisture content (or degree of saturation) -----------------------------------------------------------------------------------• Stiffness of materials under dynamic loading• Permanent strain of the materials under dynamic loading• Bearing strength of the materials under static loading• Durability of the materials• Permeability of the materials
3. - 7. are Material Properties which affect the ability of a material to perform in the pavement under the state conditions of 1. and 2.
Background for WP2
10
Characterising these mechanisms has lead to the development of specialised testing systems (eg, repeated load triaxial, RLT) and procedures to better understand material performance by simulating the action of pavement loading.
Asphalt
Basecourse 1
Subgrade
Basecourse 2
Subbase
Surface Wheel Load
STRESSES APPLIED TO A MATERIAL ELEMENT IN THE PAVEMENT
E1
E2
E3
E4
E5
E6
Simple tests• The simple, empirically-based classification tests were
found to aid in material quality assessment, but failed to clearly indicate overall material quality.
Repeated Load Triaxial (RLT) test• Unbound Granular Materials (UGMs) were very sensitive to
changes in moisture content for a particular grading …...
11
Findings …….
12
PERMANENT AXIAL STRAIN RESULTSGRANITE MATERIAL WITH 10% FINES
0
50
100
150
200
250
300
350
400
450
500
0 2500 5000 7500 10000 12500 15000 17500 20000
CYCLES
1p
-
1p
(1
00
) x 1
0-4
DDR=96.8%, RMC=43.9%
DDR=97%, RMC=70.9%
DDR=97%, RMC=75.3%
HIGH STRAIN SUSCEPTIBILITY
MODERATE STRAIN SUSCEPTIBILITY
LOW STRAIN SUSCEPTIBILITY
Example ….
13
Repeated Load Triaxial (RLT) test• Permanent deformation characteristics of different UGMs
found in the wheel tracking tests were comparable with those determined by RLT testing ……..
• Marginal-type materials could not support the high stress loadings applied in the present draft of the CEN RLT Method A. Only, high quality basecourse-type materials will be able to be assessed at the preconditioning and resilient modulus stress stage paths currently presented in the CEN procedure.
Wheel Tracking (WT) test• For a very thinly surfaced unbound granular pavement, the
wheel tracking tests showed between 73 to 95% of the total layer permanent deformation resulted in the upper half of the basecourse layer
Findings …….
14
PERMANENT STRAIN RATE RESULTS
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0 10 20 30 40 50 60 70 80 90 100
RELATIVE MOISTURE CONTENT (% of OMC)
PE
RM
AN
EN
T S
TR
AIN
RA
TE
PA
RA
ME
TE
R
d p
/dN
x 1
0-5
(%
/cyc
le)
Gneiss, Control GradingGranite, Control GradingLimestone, Control GradingUK RCC&A Supply GradingGneiss, WT testGranite, WT testLimestone, WT test
measured at 3000 cycles
FAILED
HIGH STRAIN SUSCEPTIBILITY
LOW STRAIN SUSCEPTIBILITY
Aim:to study variability of in-situ conditions in pavements (surveya number of trial pavements in various countries), in particular:• key aspects are temperature, rainfall, moisture changes within
pavement• aspects depend on climate, topography, etc
Why do we need to know this?• To investigate seasonal and transient variations in moisture within
pavement layers in time.
• to perform a sensitivity analysis on pavements to determine effect of material moisture changes (resilient modulus --> strains).
• in order that the results from WP2 (lab.testing) may be interpreted correctly as part of WP4 (modelling of pavements). 15
Work Package 3
16
Seasonal Moisture VariabilityDifficulties were encountered in the installation and operation of TDR proves on some sites.
The evidence from the experimental sites suggests that more work is needed to develop equipment which can confidently monitor low moisture contents (<4%) in granular materials.
However, generally the measurement of moisture content using this method was very effective at the Test Sites……..
Findings …….
a) Measurement of Layer Thickness b) Sub-base TDR and Compaction Equipment
c) Measurement of Depth to TDR Probe d) Installation of TDR Probe in BasecourseLayer
(e) Datalogger and Solar Cell Mast and f) Compaction of Surface DressingInstrumented Layer Pit after Compaction of Unbound Layers
17
TDR
INSTALLATION
18
Seasonal Moisture VariabilityIn all European countries in which pavements were monitored for seasonal moisture changes it was observed that:
• the variation in all structural layers followed clearly defined seasonal variations, with the moisture content being the highest in autumn and spring ……..
Findings …….
0
5
10
15
J J A S O N D J F M A M J J A
Gra
vim
etri
c m
oist
ure
con
t. [
%]
0
10
20
30
40
Pre
cip
itat
ion
[m
m]
precipitation
Base course 2, D =15 cm
Subbase 1, D = 25 cm
Subbase 2, D = 45 cm
Lighter Rainfall period
Start of freeze/thew
Probe location depth
Gravimetric moisture content in a road in Iceland plotted along with the daily precipitation
19
Heavy rainfall period
End of freeze/thaw
Freeze - Thaw Measurements in Icelandic road
20
0
20
40
60
80
100
120
10'98 11'98 12'98 1'99 2'99 3'99 4'99 5'99
Month
Dep
th (
cm)
Frost ThawFrost
Seasonal Moisture VariabilityIn all European countries in which pavements were monitored for seasonal moisture changes it was observed that:
• moisture variations between 40% to 90%+ of mod. Proctor OMC could occur in different pavement layers during the course of a year, viz:• Finland, Site FI.1• base 1 layer, RMC = 42% to 81%• base 2 layer, RMC = 35% to 98%• sub-base layer, RMC = 122% to 151%
• France, (test track)• base layer, RMC = 42% to 98%
• Iceland, Sites IS.1-3• base 2 layer, RMC = 67% to 133% stand. Proctor OMC• sub-base 1 layer, RMC = 44% to 131% stand. Proctor OMC• sub-base 2 layer, RMC = 54% to 119% of standard Proctor OMC
21
Findings …….
Seasonal Moisture VariabilityIn all European countries in which pavements were monitored for seasonal moisture changes it was observed that:
• moisture variations in different pavement layers during the course of a year ….. continued, viz:• Ireland, Site EI.1-2• base layer, RMC = 43% to 68%• sub-base layer, RMC = 43% to 68%
•Portugal, Site PT.1• sub-base layer, RMC = 27% to 97%
22
Findings …….
23
Seasonal Moisture VariabilityThrough monitoring two road sections in Finland, it was found that:
• pavement structures through cuttings yield a moisture content slightly higher, but with a lower variation, compared to pavement structures founded on an embankment.
• for structures through cuttings, water has the opportunity to flow into the pavement layers particularly if deep side drains are not installed
Findings …….
24
Seasonal Moisture VariabilityRoad construction aspects to be considered include the:
• provision of an adequate depth of impervious bituminous surfacing and a sufficiently wide "hard" shoulder, with the same surfacing as the carriageway, to reduce variations in moisture content in unbound base and sub-base layers ……..
• Formation and taping of the shoulder of the road to prevent “drainage channels” forming next to the seal ……..
Findings …….
25
3m wide “hard” shoulder at Site E1.3 in Ireland
Inadequate shoulder formation at Site in Iceland …. “drainage channel” adjacent to seal
3m wide “hard” shoulder
Aim:to analyse Project data/outcomes, in particular:• material models for stress-strain behaviour (Boyce, Dresden)• examine data for instrumented full-scale pavements• compare strain predictions from computer modelled pavements (using
material models) with measured strains in the pavement• examine modelling in detail (validity, influence of MC, etc)
Outputs?• information regarding material/pavement performance from trials• evaluate some actual pavements using different model techniques (linear
elastic, non-linear elastic, FE) ---> suggest merit of different approaches
26
Work Package 4
0
10
20
30
40
50
60
70
80
90
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Dep
th (c
m)
Direction of the truck mouvement (x-x)
Vertical displacement (strain) transducers, GM
Vertical displacement (strain) transducers, SG
Tensiometers (suction) in GM & SG
Vertical pressure transducer, SG
Long. & transv. strain gauges, BM
Thermocouples (temp), BM
Full-scale experiment: typical pavement structure and instrumentation
86mm
430mm
27
Bituminous mat.
Unbound Granular mat.
Subgrade mat.
analytical approaches being used for modelling pavements:
(1) all materials are linear elastic
(2) bit. layer linear elastic, GM non-linear elastic (Boyce), SG linear elastic
(3) bit. layer linear elastic, GM non-linear elastic (Boyce), SG non-linear elastic (Boyce)
(4) bit. layer visco-elastic, GM non-linear elastic (Boyce), SG non-linear elastic (Boyce)
28
Full-scale pavement loading experiment: the LCPC site
29
Pavement ModellingAn intermediate thickness of the bituminous layer (85mm) indicates:
a "limited" non-linear, load-dependent response of the flexible pavement (which can be further limited by cold test conditions causing stiffening of the bituminous layer).
a strong strain measurement dependence on the loading speed for speeds up to 40km/h
A thick bituminous layer (295mm) ) indicates: a a very linear response of the pavement to different
levels of load a strain measurement dependence on the loading
speed for very low speeds up to 15km/h
Findings …….
Aim:to analyse Project data/outcomes, in particular:• analysis of all project information (broad picture, key findings)• cost-benefit analysis (factors include pavement material properties,
traffic loadings, pavement life [modelling], material costs)• links with other projects (eg. COST337, AMADEUS, ALT-MAT, etc)• strong dissemination mechanisms
Outputs?• present COURAGE findings (reports, seminar UNBAR, papers, etc).• WWW interface for dissemination.
http://www.civeng.nottingham.ac.uk/courage/• design procedure for prediction of pavement performance based on
laboratory data.• draft of design and practice guide for material usage in pavements. 30
Work Package 5