ABSTRACT
Pavements structures consist of several layers, and their structural behavior strongly depends on the bonding condition between layers. Despite this fact, in the French pavement design method (like in other methods), only very simplified interface conditions are taken into account: the interfaces are considered either fully bonded, or fully debonded. This paper presents results of the monitoring of an instrumented bituminous pavement section, built on a motorway, in France, where interface behavior has been monitored by strain gages, placed at different levels in the pavement. Continuous strain monitoring, under real traffic, for 18 months, has shown that the degree of bonding between pavement layers can change with temperature: at low temperatures, the strain measurements indicate a fully bonded behavior, but at high temperatures, high horizontal tensile strains are measured in the upper pavement layers, showing evidence that the degree of bonding between pavement layers is reduced. Similar results had been obtained previously at IFSTTAR in accelerated pavement tests. To analyze the behavior of this instrumented pavement section, a classical multi-layer linear elastic model, and a viscoelastic model have been used. In both cases, each interface has been described as a thin elastic layer with a low modulus, varying with temperature. The best predictions have been obtained with the viscoelastic model. Consequences of the variable degree of bonding between pavement layers on the fatigue life of the pavement are discussed.
