ABSTRACT
A French national project, named REVES, started in 2015. The project aims at designing a thin railway track, with neither ballast nor sleepers, in order to increase the gauge in tunnels. The goal is to obtain a cost-effective way to increase the gauge of old tunnels which were initially not adapted to modern freight gauge. Inside the project, a PhD thesis started with the purpose of studying a railway infrastructure design that replaces ballast and sleepers by an asphalt concrete layer. One main challenge of the thesis is to predict the behaviour of asphalt concrete under freight loadings. Special attention is given to creep under heavy and static (or very slow) loads, due to the viscoplastic nature of asphalt concretes. A viscoplastic model, based on the Perzyna formulation, was developed to describe the irreversible creep behaviour of asphalt concretes. Model parameters were identified by means of triaxial creep tests, performed at constant temperature. The model was implemented in FEM software Cast3M in order to perform structural computations. Some simulations of railway structures including an asphalt concrete layer were performed. A first observation is that under static or slow loading condition, stresses inside the structure redistribute over time, leading to eliminate any tensile stresses. The stress distribution tends toward a compressive state similar to those found in unbound materials. Then the final stress states are compared with the experimental stress domain initially used to identify the model parameters to validate the relevance of the whole approach.
