Presentation on theme: "COnstruction with Unbound Road AGgregates in Europe."— Presentation transcript:
COnstruction with Unbound Road AGgregates in Europe
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: 3 ie, 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) ….
of the Technical Work Packages ……. 6 KEY FINDINGS
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. E1E1 E2E2 E3E3 E4E4 E5E5 E6E6
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 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 …….
Aim: to study variability of in-situ conditions in pavements (survey a 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 Variability Difficulties 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 …….
18 Seasonal Moisture Variability In 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 …….
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
Seasonal Moisture Variability In 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 Variability In 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 Variability Through 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 Variability Road 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
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 Modelling An 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