Characterization of unbound materials by following an empirical and mechanistic-empirical approach for the construction of internal roads for solar and wind farms

In this century, the importance of energy has heightened due to the depletion of natural resources and the environmental impact caused using fossil fuels. The pressing need for alternative energy sources to replace natural gas and oil has become clear. The transition to green energy systems, which rely on renewable sources like sunlight, wind, hydro, and geothermal energy, has become a crucial initiative. These systems offer long-term energy solutions while reducing harmful environmental effects. This master's thesis aims to characterize the unbound material used in constructing internal roads capable of accommodating heavy vehicles during the construction of renewable energy plants. The study utilizes both empirical and mechanistic-empirical approaches. These heavy vehicles are necessary for transporting large equipment and components such as hub assemblies, blades, and generators. Consequently, road design must consider the expected heavy vehicle traffic during the farm construction. The thesis work commences with using two types of materials extracted from a wind farm. By employing both empirical and performance-related laboratory tests, the influence of water content and stress state was highlighted for the investigated materials. To evaluate a soil's dry unit weight and dry mass, the optimum water content was used as a parameter. These values allow material compaction to achieve the desired dry density and bearing capacity. The compacted specimens are then subjected to triaxial cell testing. The triaxial test aims to simulate the stress-strain behavior induced by traffic loads and employs a rational approach to characterize the unbound material through the resilient modulus. After obtaining the stiffness behavior, which characterizes the response of granular material under loading, considering seasonal variations, a multi-layer elastic system is adopted as a structural reference model. Data obtained in the experimental investigation were then used to design the internal road network of an existing wind farm.