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

Abstract

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 Kahramanmaras 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' class20 % (1/3 <= S/C <1); 'C' class-16 % (S/C 1/1); 'E' class14 % (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-phi, 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.