Projekt BVFF - publicerade
 
BVFF nummer: 
2017:1-06
Projekttitel 
Development and evaluation of performance models for unbound road materials
Projektledare/Kontaktperson 
Denis Jelagin
Telefon 
087908698
Utförarorganisation 
KTH
Medutförare 
VTI
NCC
Bakgrund 
The goal of the project is to conduct a doctoral study at KTH on the further development and validation of performance models for the road unbound layers. The experimental and validation part will be performed jointly by KTH and VTI. The models developed will provide a quantitative link between unbound material performance and material design parameters, i.e. gradation, stone’s shape and mechanical characteristics. The primary focus will be on the models capturing the effect of materials gradation on its performance. Project outcomes will be incorporated into the unbound material performance models available at VTI and accordingly into ERA Pave design tool.
The project builds on results attained in several projects recently completed at KTH and VTI. In particular, models developed at VTI under the PhD projects of Drs. Rahman and Salour allow to predict deformation of unbound layers at cyclic loading. The framework developed at KTH within the “Obundna lager (dimensioneringsmetodik för spårbildning)” project presents an alternative to establishing continuum material models; based on packing theory combined with micromechanical considerations it allows to identify the load carrying part of the gradation and evaluate the parameters describing the materials structure quality. No model is available so far however linking quantitatively the material parameters to its resilient and permanent deformation performance and degradation. The proposed project aims to close this gap.
Sammanfattning 
The primary goal for the project is to develop and validate improved performance prediction models for unbound layers in the road structure. The developed and experimentally validated models, will allow to explicitly link unbound materials parameters to the expected performance. The focus of the project will be on models capturing the effect of materials gradation on its performance. The project builds up on research results attained in several research projects recently completed at KTH and VTI. Project outcomes will be incorporated into the unbound material performance models available at VTI and accordingly into VTI’s pavement design tool ERA Pave.
Förväntat resultat 
In addition to the theoretical and experimental insight to the mechanics of the unbound granular layers in the road structures, the project’s main outcome will be a tool for performance prediction and mechanics based design of the unbound materials, including:
- Predictive models for the resilient modulus and permanent deformation accumulation incorporating explicitly materials gradation, degree of saturation as well as stone’s characteristics (i.e. shape, strength and mechanical properties).
- Model describing the progress of aggregate breakage and wear as a function of aggregates strength, shape and gradation.
- Design tool facilitating finding the optimal gradation and unbound layer thickness for a given aggregate type, road structure and loading conditions.

Accordingly, the projects results will help to close the gap outlined in introduction. In order to facilitate the use of results by both practitioners and researchers, two levels of deliverables are planned. Namely, the calibrated DEM-based analysis framework will be available at KTH and VTI. At the same time, based on modeling and experimental results obtained under the project, a simplified equations will be established and validated, incorporating the effects unbound material characteristics into the unbound layers performance models developed at VTI. This will allow direct integration of the project results into the VTI’s pavement design tool ERA Pave.
Plan för resultatspridning och implementering 
In order to ensure that the results of the project are communicated to the research community and to the users, the following steps will be taken:

- A user reference group will be formed at the start of the project. The reference group will consist of representatives of the following authorities/companies: Trafikverket (Robert Karlsson), Skanska, NCC (Jonas Ekblad), Peab. Three times a year, a detailed presentation will be given to the reference group.

- Results of the project will be published in several scientific papers and summarized in a PhD-thesis.

- The results achieved in the project will also be presented at SBU and Road2Science events

- Results will be as well presented in national and international conferences.

Tidsramar 
The project is expected to take 4 years and will start as soon as the doctoral student will be recruited.