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 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.