Sarkisian H. Substantiation of the required strength of non-rigid pavement by the marginal roughness criterion

The thesis offers a new solution of the relevant scientific and practical issue of assigning the required general modulus of elasticity of non-rigid pavement, taking into account the criterion of maximum longitudinal roughness of coverage for the last year of operation before overhaul. Relevant theoretical and experimental studies on the interaction of a pneumatic or rigid wheel with a coating are analyzed. The analysis finds that there is a relationship between the roughness of coverage and the strength of the pavement, which opens the possibility of determining the strength of the structure of non-rigid pavement, which provides a given level of coverage for the last year of operation before overhaul. A significant disadvantage of existing solutions is the lack of consideration of the deformable properties (modulus of elasticity) of pavement. Based on the results of the analysis of existing approaches to consider the impact of vehicle wheels on the construction of pavement when overcoming the unevenness of the road surface, a calculation scheme for determining the dynamic factor. The scheme of determining the dynamic factor allows to take into account the additional load on the pavement, which occurs when the wheel interacts with the unevenness of the pavement. For the first time, the factor of bringing the mass of the “vehicle – pavement” system to the point of impact is considered when calculating the load dynamic factor on non-rigid pavement. The model of change of coverage roughness, where increase in the roughness index over time is considered as a function of such parameters. The adequacy of the developed model of changing the roughness of coverage is confirmed by statistical processing of experimental data obtained by the thesis author and other researchers on public roads with different service life, and calculated data under the theoretical model. The stress-strain state of the construction of non-rigid pavement with the use of different load dynamic factors is simulated. The results of modeling the stress-strain state of the structure of non-rigid pavement show that the tensile strength of asphalt concrete layers is the most “sensitive” to dynamic loads. The limit value of the dynamic factor under the condition of the admissible disturbance ratio is established. The paper proposes a method for determining the required modulus of elasticity of non-rigid pavement by the criterion of marginal roughness of coverage by iterations, based on a model for predicting the roughness of coverage for the last year of operation of non-rigid pavement before overhaul. To simplify the calculations, a nomogram and the procedure for determining the required modulus of elasticity of the non-rigid pavement structure by the criterion of marginal roughness of coverage using a nomogram are developed.