Engineering Classification for the Determination of the Uniaxial Compressive Strength of Carbonate Fault Rocks

The carbonate fault rocks exhibit severe transformations when subjected to fault zone deformation. The parent materials are transformed into fault rocks that comprise fragments and secondary (usually weak) matrix. In the present study, specific types of carbonate fault rocks are investigated, and their mechanical properties are quantified using a novel methodology. These types include the parent/host rock, welded fault breccias, unwelded fault breccias and matrix material. Carbonate fault rocks from western Lefkada island, Greece, were studied in the laboratory to establish a relationship between their Uniaxial Compressive Strength and their textural features, i.e., the geometrical aspects of their fragments and matrix (size, shape, distribution). The results indicate that the Uniaxial Compressive Strength of the welded/unwelded breccias is a function of the corresponding strength of their components (fragments and matrix) and the matrix ratio (the percentage of matrix in a given volume). Due to the weak nature of the matrix, the Uniaxial Compressive Strength of the matrix cannot be readily measured. Therefore, suggestions for the determination of its Uniaxial Compressive Strength based on field assessment are proposed.