Analysis of Deformation Energy Dissipation in Reinforced-Layer Pavement

Introduction. The design of road pavements for highways is a key stage of project development, directly impacting their durability and operational costs. In recent years, in the context of increasing traffic intensity and dynamic loads, technologies for strengthening roadbeds and bases, such as geosynthetic reinforcement and stabilized layers, have become widespread, making the study on their efficiency a challenge. Literature notes the practical advantages of reinforced layers — increased load-bearing capacity and reduced deformation. However, models for energy dissipation under dynamic impacts in structures with such layers are underdeveloped. Theoretical approaches to analyzing energy dissipation, including linear-elastic and viscoelastic models and finite element methods, have been primarily applied to traditional structures. Their adaptation to reinforced and stabilized layers requires further development, as there remain gaps in the quantitative comparison of efficiency by location and rigidity of reinforcements. The objective of the presented work is to analyze the dissipation of deformation energy in the structure of road pavements with different options for the arrangement of reinforced layers, and to determine optimal design solutions that contribute to increasing the durability of road pavements. To achieve this, it is required to formalize an energy dissipation model for structures with reinforcements, conduct a comparative analysis of different locations and rigidity levels of the layers. Materials and Methods. The research utilized a comprehensive approach to the analysis of deformation processes in layered media using road pavements as an example, involving both a calculation tool and modern experimental equipment. As a calculation tool, a mathematical model of a layered half-space in an axisymmetric formulation in a cylindrical coordinate system was used. It was based on the solution to the system of dynamic Lame equations and allowed for the construction of amplitude-time characteristics of vertical displacements and impact loading impulse, on the basis of which it was possible to construct dynamic hysteresis loops. The FWD PRIMAX 1500 shock loading unit was used as experimental equipment, which made it possible to register similar characteristics of the road pavement response under field conditions at a load equivalent to the calculated one. Results. The study involved numerical modeling of road pavement structures traditionally used in the Russian Federation and so-called full-depth road pavements, which were composed almost entirely of materials reinforced with binders. Dynamic hysteresis loops were constructed, and a comparative analysis of the results was provided. A numerical experiment revealed that strengthening only the subgrade layer, even without installing a reinforced base layer beneath the asphalt concrete, reduced the amount of dissipated deformation energy. It was also concluded that the elastic modulus of the underlying half-space simulating the subgrade had the greatest impact on the amount of dissipated energy. Discussion. The greatest effect, both technical and economic, can be reached by strengthening the top of the roadbed while preserving the loose layers in the base of the road structure. This solution will bring the functioning of the road surface closer to the elastic stage and at the same time reduce the risk of cracks appearing on the surface of the pavement due to an excessively rigid layer of reinforced base. Conclusion. On the basis of the constructed dynamic hysteresis loops, it is shown that a reduction in the magnitude of deformation energy can be obtained both by installing reinforced layers of the road surface throughout its entire depth, and by locally strengthening the underlying half-space layer and an additional base layer made of sand. The numerical experiment demonstrated that the use of reinforced base layers reduced the amount of deformation energy dissipation in the pavement structure by more than 2–3 times. Qualitative agreement between the experimental results and the numerical simulation results was shown.