Towards better consideration of interface behavior between asphalt pavement layers – INTERFACE

The experimental part will consist of three main tasks which are: (i) the analysis of a full-scale test carried out in a previous project on an asphalt pavement greatly instrumented within the topmost layers and at their interface, (ii) the setup of an intermediate-scale test for characterizing the interface condition between AC layers of small structures (but representative of real pavements) subjected to moving loads under well controlled environmental and loading conditions, (iii) the development or adaptation of nondestructive techniques (Falling Weight Deflectometer, triaxial accelerometry, Ground Penetrating Radar) for the assessment of interface conditions.
From the modeling perspective, the main objective will be the derivation of ad hoc constitutive laws for asphalt pavement interfaces and their implementation in Finite Element (FE) codes. So far, AC interfaces were considered through perfect bonding, perfect sliding or modeled as thin elastic or viscoelastic layers. However, these approaches failed in simulating the response of instrumented full-scale pavements tested recently at Université Gustave Eiffel. Preliminary analyzes of these pavement sections indicated that a frictional model involving the effect of normal and tangential stresses applying at the interface would be more suitable to capture their mechanical responses. Consequently, the interface laws that will be developed in this project will be based on viscoplastic friction models (continuum mechanics) as suggested by the most up-to-date research results. The effect of temperature will be carefully introduced in these models which will be implemented in FE codes to simulate the response of pavement structures including complex interface behavior and subjected to moving loads.

The results of this project will be fundamental for conventional asphalt pavements in order to find solutions to prevent premature damage to surface layers. The knowledge gained will benefit other applications such as electric roads or tramways, which are also affected by similar interface problems.

In addition, a very large open-access database will be created during the project. New interface behavior laws will also be developed.

The experimental and numerical parts will be conducted closely so that one can benefit the other whether in terms of analysis, calibration or validation. On the one hand, the outcome of this project will be valuable to classical asphalt pavements, for example to help find solutions to prevent premature damaging of surface courses. On the other hand, the knowledge gained in this project will also be useful for other applications like electric roads or tramways which are also affected by the interface issues described above.

- Two thesis reports by doctoral students involved in the project
- Publication of articles in scientific journals and technical/professional journals
- Presentation of work at scientific conferences and technical seminars
- Dissemination of open source calculation codes
- Creation of a freely accessible database
- Drafting of an
- End-of-project report

The present project will focus on understanding and modeling the behavior of interfaces between asphalt concrete (AC) layers in pavements subjected to traffic loads. This aspect of pavement mechanics is important because the interface behavior sorely affects the strain and stress distributions in the structure, particularly in the surface courses which durability represents a current research challenge. A particular attention will be paid to the effect of temperature that drastically impacts the AC interface behavior. According to recent full-scale tests, another complex feature to be considered is the occurrence of horizontal displacement jumps between interface lips under the pass of traffic loads. This was already observed in areas where perfect bonding was expected. This feature will develop depending on parameters like for example temperature, the type of interface or the normal stress applied to the interface, as suggested by the latest research. Moreover, discontinuities of the horizontal displacement at the interface is more likely to occur after its rupture. The detrimental consequence of these displacement jumps is the development of flexural-induced tensile strain at bottom of the surface layer that can be of high magnitude and cause damage to this layer which is not designed to withstand extension. The interface behavior is not well understood yet, nor are the mechanisms that lead to an operating mode with slipping or not. Consequently, the main objective of the present proposal is to conduct cutting edge experimental and modelling research to improve fundamental and practical knowledge on the mechanisms involved in interface response and behavior.
The experimental part will consist of three main tasks which are: (i) the analysis of a full-scale test carried out in a previous project on an asphalt pavement greatly instrumented within the topmost layers and at their interface, (ii) the setup of an intermediate-scale test for characterizing the interface condition between AC layers of small structures (but representative of real pavements) subjected to moving loads under well controlled environmental and loading conditions, (iii) the development or adaptation of nondestructive techniques (Falling Weight Deflectometer, triaxial accelerometry, Ground Penetrating Radar) for the assessment of interface conditions.
From the modeling perspective, the main objective will be the derivation of ad hoc constitutive laws for asphalt pavement interfaces and their implementation in Finite Element (FE) codes. So far, AC interfaces were considered through perfect bonding, perfect sliding or modeled as thin elastic or viscoelastic layers. However, these approaches failed in simulating the response of instrumented full-scale pavements tested recently at Université Gustave Eiffel. Preliminary analyzes of these pavement sections indicated that a frictional model involving the effect of normal and tangential stresses applying at the interface would be more suitable to capture their mechanical responses. Consequently, the interface laws that will be developed in this project will be based on viscoplastic friction models (continuum mechanics) as suggested by the most up-to-date research results. The effect of temperature will be carefully introduced in these models which will be implemented in FE codes to simulate the response of pavement structures including complex interface behavior and subjected to moving loads.
The experimental and numerical parts will be conducted closely so that one can benefit the other whether in terms of analysis, calibration or validation. On the one hand, the outcome of this project will be valuable to classical asphalt pavements, for example to help find solutions to prevent premature damaging of surface courses. On the other hand, the knowledge gained in this project will also be useful for other applications like electric roads or tramways which are also affected by the interface issues described above.