Engineering-Geological Characteristics of Quaternary Deposits in the Southern Caspian Sea Shelf
Abstract:
This study characterises the engineering-geological properties of Quaternary deposits in the southern Caspian Sea to provide a reliable basis for offshore geotechnical design. A total of 300 core samples from 70 boreholes across 45 offshore sites in the Baku Archipelago, the Apsheron–Pre-Balkhan zone, and the Turkmenian and Iranian sectors were examined. Undisturbed samples collected during 1984–1996 and 2019–2022 were tested using standard geotechnical methods to determine their physical, mechanical and mineralogical character istics. The deposits are dominated by clays and loams, with subordinate sands. Clay-rich units comprise up to 50% of the sequence, particularly in deeper basins. Fine fractions (<0.005 mm) range from 32% to 93%, with hydromica and montmorillonite as the principal clay minerals. Carbonate contents vary from 0% to 39% and increase in areas influenced by mud volcanoes. Measured properties include natural moisture contents of 0.15–0.95, dry densities of 1.0–1.7 g/cm³ and porosities of 35–70%. The soils show low to moderate plasticity and are generally normally consolidated. The angle of shearing resistance ranges from 7° to 29°, and cohe sion from 0.005 to 0.175 MPa. The results support prediction of engineering parameters from limited data and strengthen seabed stability and foundation assessments for the Caspian shelf.
