Operation Behavior of Road Pavements in the Hypothesis of Bound Road Layers CIPRIAN COSTESCU, ALEXANDRA CIOPEC, PAUL MARC Department of Land Communication Ways, Foundations and Cadastral Survey Politehnica University Timisoara Ioan Curea Street, no. 1A ROMANIA ciprian.costescu@upt.ro, alexandra.ciopec@upt.ro, paul.marc@upt.ro Abstract: - Cooperation between layers represents one of the current issues regarding road pavements analysis on their operational behavior under traffic loads. The bound between road layers, by most of calculation methods, including the Romanian ones, is considered perfect. It is hard to say how true this statement is, but it is expected that it is unlikely for this bound to be “perfect” for the entire service life of the road pavement. The road pavements are calculated depending on different parameters (traffic, bearing capacity of foundation soil, the characteristics of materials in road pavement composition, climate, etc.) so that every layer will only be requested on its own level of bearing capacity. Specific stresses and strains are transmitted in different layers depending on the characteristics of component materials and the bound between them. Starting from the research concerning the binding hypotheses between interfaces, based on the ALIZE elastic pattern, which showed that, depending on the cooperation between road layers, the life of a road pavement can vary within very large limits, the paper intends to analyze the impact of the binding hypotheses between road layers upon the stress and strain condition within road complexes based on mathematical modeling. Key-Words: - road layer, road pavement, bound, deformation, interface, hypothesis 1 Introduction One of the present issues concerning the analysis of the road pavements behaviour in operation is represented by the cooperation of layers [1]. If the accumulated efforts are over the permitted limits in the road pavements the deformations of the layers become permanent. When the layers are bound a road pavement constitutes a monolith assembly, in which every layer is being deformed, but not independently, according to its characteristics and in relation with the other layers with which it is bound. When the layers are not bound, each road layer works independently according to its own properties. In this case, the deformations and tensions are much more important than in the hypothesis of the bound layers, especially at the interfaces. Studies carried out on certain road pavements have shown that, depending on the cooperation between road layers, the life span of a road pavement can vary within large limits. The research was carried out on a flexible road pavement whose composition is shown in figure 1 [2]. There is the additional risk of the layers sliding one on top of the other under traffic stress (fig. 2). The unbinding of layers results in a less durable pavement or in additional maintenance works. asphalt granular foundation 15 years 4 years 5 years 6 months material bituminous layer [15 cm] mixture [8 cm] asphalt mixture [8 cm] asphalt mixture [8 cm] asphalt mixture [8 cm] soil foundation soil foundation soil foundation soil [45 cm] granular material [45 cm] granular material [45 cm] granular material [45 cm] bituminous layer [15 cm] bituminous layer [15 cm] bituminous layer [15 cm] Fig. 1 Theoretical life span of the road pavement The onset of degradations due to poor binding between layers will lead to a costly maintenance, since the application of a strengthening layer is required or the milling of the poorly bound layers and their replacement. Thus, based on these facts, the significant technical and economical importance of the bound interfaces can be demonstrated. It is true that besides the hypotheses concerning the bound road layers, the operation behaviour of road complexes is strongly influenced by the quality of the foundation soil. So, the presence of the foundation grounds with a reduced bearing capacity Advances in Environmental Development, Geomatics Engineering and Tourism ISBN: 978-960-474-385-8 226