Effects of Olivine Alteration on Micro-Internal Structure and Geomechanical Properties of Basalts and Strength Prediction in These Rocks

Understanding the variations of the geomechanical properties of rocks in geotechnical projects from the perspective of their micro-structures and alteration conditions is crucial for ensuring the safety and long-term sustainability of rock engineering (e.g., tunnels, slopes, mining). This study was carried out on basaltic rocks from the Akcakale and Mersin vicinities in Trabzon City to investigate the geomechanical and mineralogical properties in comparison with the uniaxial compressive strength (UCS). This study was conducted in three different locations (A1, M2, and M3) where the basaltic rocks outcrop belongs to the same lithological formation. During this study, quite different results were obtained from the basalt samples taken from different sites and the reasons for these differences were examined by petrographic, SEM (Scanning Electron Microscopy), and EDS (Energy Dispersive Spectroscopy) analyses. Since the number of comprehensive studies on basalts is very limited, this study aims to investigate practical and useful equations in the estimation of the UCS for various alteration conditions. Statistically, significant relationships were observed between geomechanical properties with the UCS and serpentinization rate (SR). This study revealed that the serpentinization of the olivine mineral is the most important factor causing the differences in the experimental results. The proposed equations for estimating the UCS are particularly significant for geotechnical applications where direct sampling is challenging, such as in weak-rock environments.