The geotechnical evaluation of sandstone-claystone alternations based on geological strength index.

The aim of this study is to classify heterogeneous deep-sea sediments (including sandstone and claystone) according to the geological strength index (GSI). Forty-nine locations have been selected from excavated Miocene deep-sea clastic sediments bearing slopes from the Kahramanmaraş Basin (SE Turkey). Six rock classes are determined based on sandstone/claystone ratios (S/C). Those rock classes and their percentages are 'B' class of 39 % (1 < S/C ≤10); 'D' class-20 % (1/3 ≤ S/C <1); 'C' class-16 % (S/C 1/1); 'E' class-14 % (1/10 ≤ S/C <1/3); and rest 11 % formed by 'F' class (tectonically deformed), 'G' class (S/C <1/10), and 'A' class (S/C >10). Four different groups of rock are separated according to GSI based on rock classes and discontinuity surface conditions ('A-B' class, GSI > 40; 'C' class, 35 ≤ GSI ≤ 40; 'D-E' class, 25 ≤ GSI < 35; 'F-G' class, GSI < 25). The lower values of the Mohr-Coulomb and strength parameters of rock mass (cohesion-c', internal friction angle- ϕ, and deformation modulus-Em) are observed in the 'E-D' classes due to high clay content, while higher values in the 'A-B' classes due to high sand content. [ABSTRACT FROM AUTHOR]