Laboratory tests of unbound aggregate pavement base under cyclic loading and the impact of ground deformations caused by mining

The aim of the article is to determine the changes in the stiffness of an unbound aggregate base layer subjected to cyclic loading and the impact of mining deformation. The article presents the characteristics of the scale of changes in the stiffness of both the pavement layers and the subgrade for a category III mining area, i.e., for horizontal strains up to 6 mm/m. The characteristics are based on previous experience, which takes into account the impact of mining deformations that occurred in a category II mining area. The aim of the article was achieved based on the results of laboratory tests. These tests were conducted on a test stand that enables the simulation of the cyclic loading of the surface of a tested layer system and the horizontal strains of the ground. The cyclic loading caused by the rigid plate simulated the movement of vehicles. Numerical analysis of the issue for the conditions of laboratory tests was also carried out. This analysis was aimed at estimating the change in the parameters of individual layers in the tested system in subsequent stages of the laboratory tests. The results of the tests and analysis show that for horizontal tensile strains of 0.0–6.0 mm/m, a reduction in the elasticity moduli to approximately 35–45% for unbound aggregate and approximately 70% for fine-grained layers may occur.