EXPERIMENTAL STUDY OF BITUMINOUS MIXES, FATIGUE PHENOMENON UNDER TANDEM SOLICITATION AT LARGE STRAIN

Abstract

Asphalt mixture in pavement is exposed to a fatigue phenomenon which often causes its failure after a certain period of operation. Conventionally this is simulated in the laboratory by a mechanical stress in the form of continuous sine under the effect of a single axle. In recent years the designs of aircraft and large vehicles have changed a lot, given the needs in volume and transport capacity requested. We often see the tandem axles, tridem axel etc. Damage of asphalt mixture is related to vehicle characteristics (number and loads per axle, suspension type, speed, tyre type and configuration...); rest period, temperature and pavement material properties. Modern conceptions of jumbo aircraft type (e.g. Airbus A380, B777 etc...) and new designs of heavy trucks have imposed other forms of solicitation. This type of loading is dual axles with higher strain amplitude. Currently the road pavement and airport asphalt are subject to high levels of strain (or stress) of short duration at each passage of axles. The choice of the structure and the sizing of a roadway require consideration of several technical criteria, economic and geographic, such as heavy traffic and its developments. In this context, fatigue tests were carried out under load at large deformation (high strain amplitude) and can have multipeak shapes (tandem low valleys between two successive peaks). These tests were used to assess and compare the effect and aggressivity of large amplitudes of strain in terms of life, according to two types of signals (single axle and tandem).