Effect of geogrid usage on railway pavement design

The use of geosynthetic materials has become widespread in the world and in our country in recent years, as it is a fast and economical option in solving geotechnical problem on railway pavement sub-structure. It is claimed that geogrids, which is a type of geosynthetic material, are effective in strengthening weak soils, reducing layer thicknesses, extending the service life of the structure, cost of maintenance in transportation infrastructure and pavement projects. In a railway pavement; the determination of the stress and deformations occurring in the railway line, forming of the layers and the loads applied on the railway line is obtained as a result of long efforts with the help of laboratory conditions or field applications. The use of finite element method in determining the stresses and deformations required for design has been increasing significantly in recent periods. In this study; the possible effects of a single row geogrid placed between the sub-ballast layer and the subgrade on the railway pavement structure were investigated. All of the analyzes throughout this research were made with the finite element software ANSYS 2020 R2. For different axle loads, geogrids with different properties, different sub-ballast layer thicknesses and subgrades with different properties, 96 different analyzes were carried out both without geogrids and with geogrids. As a result of these analyses, the stress and deformation values occurring on the horizontal line formed at the upper boundary of the subgrade were measured. The results obtained have shown that the use of geogrid material between the sub-balast layer and the subgrade could significantly contribute to reducing the deformations and reducing the thickness of the sub-balast layer. While the geogrid material is more effective in designs with weak subgrade properties, the effect of the geogrid decreases as the subgrade properties improve. Due to the cost of infrastructure improvement methods, it is thought that the use of geogrids on weak soils will provide cumulative advantages. In addition, as a result of the cost analyzes made makes a great contribution on the use of geogrid, such as shortening the construction period, extending the service life of the structure, ease of application and reducing the frequency of maintenance, support usability. As a result, it is seen that this applied method and the obtained data could be used as a guide for a pavement to be designed to safely carrying the applide load ont the structure, resisting atmospheric conditions and creating more economically advantageous design parameters.