Engineering geological evaluation of weathered limestones and dolomites quarries in Gebze (Türkiye)

Weathering can have significant impacts on the geoengineering properties of limestone and dolomite, leading to notable changes in their characteristics and behavior. In this study, two aggregate quarries located in Gebze, Türkiye were investigated to understand the weathering characteristics of limestone and dolomite. In the context of this study, a simple chemical index to identify weathering grades of limestone and dolomite was proposed. To propose this abovementioned weathering grade index, not only various analyses, including mineralogical, petrographic, chemical, physical and mechanical investigations, but also field studies and in situ observations were considered. In terms of field observations, the studied rocks are primarily gray in color, but a brownish red color dominates weathered rocks. Along the rock mass, it was also clear that the spacing of discontinuities decreased while the apertures increased due to weathering. The number and geometry of karstic cavities that formed as a result of chemical changes are also highly distinctive properties for determining weathering, particularly for certain weathering grades. In terms of laboratory tests, on the other hand, as weathering increased, the specific gravity decreased, whereas the unit weight and water absorption values increased for the studied rock samples. Significant correlation coefficients (R² > 0.80) were obtained from the relationships between the Weathering Index for Carbonate Rocks (WICR) values and the corresponding laboratory tests, i.e., loss on ignition, dry unit weight, specific gravity, and uniaxial compressive strength. The mechanical properties also considerably decreased with increasing weathering. This paper also discusses the typical and dominant weathering profiles observed for limestone and dolomite weathering.