The introduction describes the general characteristics of the work, substantiates the relevance of the dissertation topic, formulates the purpose and objectives of the research. The scientific novelty of the work is noted, the main scientific results are given, the practical significance of the obtained results and their directions of introduction into production are shown.
The first chapter of the dissertation deals with the state of the question of ensuring the durability of asphalt concrete layers of reinforcement of non-rigid road clothing. The paper analyzes the modern solutions for increasing the durability of asphalt concrete layers of reinforcement of non-rigid road clothing. According to the results of the analysis of researches of famous scientists, it can be concluded that the analytical-calculating device intended for the prediction of the stressed-deformed state of layers of road clothing does not take into account the joint action of horizontal normal and vertical tangential stresses during fracture when assessing their durability. It has also been found that in many approaches to predicting longevity, solutions to the theory of elasticity have been used. However, the stress-strain and limiting states of the roadwear construction are significantly dependent on the thermo-rheological properties, which reflect the effect of the load time at different temperatures on the overall strength of the structure. Recently, researchers have begun to pay attention to the thermo-rheological properties of materials, but the studies carried out are disparate in nature, which still has not allowed to develop a method of evaluation of the stress-strain state of asphalt concrete layers of non-rigid road clothing on a single methodological basis.
In the second chapter, theoretical studies of the fracture resistance of asphalt concrete layers are performed. As a result of theoretical studies, a mathematical model has been refined to describe the limiting state of asphalt-reinforced layers of non-rigid road clothing. On the basis of it, the calculated schemes of operation of asphalt reinforcement layers were developed and analytical dependences were obtained to describe their limiting state, taking into account the joint action of horizontal normal tensile stresses and vertical tangential stresses arising during the passage of vehicles. Based on the applied theoretical aspects of the study, a method for calculating the durability of asphalt reinforcement layers was developed, taking into account the joint action of horizontal normal and vertical tangential stresses on fracture in the reinforcement layers, as well as taking into account the thermo-rheological characteristics of road-building materials.
The third chapter describes the experimental studies that consisted of laboratory testing, numerical experimentation, and field surveys. According to the results of laboratory tests, the thermo-rheological properties of asphalt concrete are determined, the influence of the rate of deformation of the samples on the value of asphalt concrete strength is shown, and the influence of vertical tangential stresses on the tensile strength of the asphalt concrete is determined. The calculated characteristics of reinforced asphalt concrete were also established. The numerical experiment established the effect of daily and seasonal temperature fluctuations on the durability of asphalt concrete reinforcement layers. The results of the calculation show that the durability of asphalt concrete layers can be reduced by 1.5-2.0 times, with repeated actions of short-term loads, when the coating temperatures will be equal to 10 ° C or 25 ° C. During the field experiments, the behavior of the asphalt concrete was performed. reinforcement layers using various structural and material science solutions.
The fourth chapter deals with the practical application of research findings. For practical realization of research results the following are developed:
1) Method of calculation of asphalt concrete coatings of increased durability for resistance to fatigue fracture from tensile bending;
The essence of the technique is to establish the maximum amount of application of loads on asphalt pavement of non-rigid road clothing, depending on the traffic conditions, on monocyclic loads at the time of action tn ≥0.1 s or for a binary load cycle at tn1 ≥ 0.1 s and tn2 ≥ 10 with.
2) Method of calculation of layers of reinforcement of non-rigid road clothing with the use of reinforced asphalt concrete.
The essence of the technique is to replace the thickness of a part of asphalt concrete layers, between which is reinforced material, equivalent to a layer of appropriate thickness and design characteristics. Next, the multilayer construction is reduced to a two-layer structure and the limit state criterion is calculated.
