Investigation of dynamic behaviors of high-speed railway infrastructure in cold climate regions

Infrastructure systems should be investigated due to certain concerns about the maintenance and repair of completed or ongoing projects in high-speed railway systems, which are becoming increasingly widespread in our country. Since seasonal temperature differences cause structural changes in the ground, they also cause changes in the physical and mechanical properties of the ground. Therefore, thermal effects on the ground should be taken into account in engineering designs made in cold climate regions. In this thesis, it is aimed to investigate the behavior of the infrastructure ground under dynamic analysis by modeling the elements of an existing high-speed railway infrastructure in cold climate regions. For this purpose, the climate and geological characteristics of the Ankara-Eskişehir line, where the railway infrastructure systems used in the modeling are located, are revealed. Then, the physical and engineering properties of the soil type to be numerically modeled in the subsoil layer were determined before and after different freeze-thaw cycles. Finally, three-dimensional (3D) modeled high-speed rail geometry was created with the ANSYS finite element program, each material properties were defined, modeled with EXPLICIT dynamic analysis under different freeze-thaw cycles, and engineering behaviors were revealed in different boundary conditions. As a result of the experimental studies, after the maximum freeze-thaw cycle, the UU triaxial compressive strength of the soils decreased by 19%-40%, the elasticity modulus by 30%-40%, and the cohesion decreased by 50.28%, while the internal friction angle increased by 4.85%. Modeling results showed that freeze-thaw cycles exert significant effects on both deformation and dynamic shear stress. It has been observed that the deformation values are higher in the region up to the endpoint where the wheel moves, while it remains at a lower amount at the edge outside the movement area. Freeze-thaw cycles were determined to reduce the maximum dynamic shear stresses of the soil by 10.85%, 7.43%, and 19.44% under the investigated boundary conditions.