Geological–geotechnical characterisation of Sarapuí II clay

•The geological–geotechnical characterisation of Sarapuí II clay has been presented.•Results of chemical analyses and mineralogical analyses, organic content values and index parameters have been presented.•Compressibility and strength parameters have been provided.

The paper presents the geological–geotechnical characterisation of the very soft organic plastic slightly overconsolidated Sarapuí II clay. Dissipation tests showed no artesian pressure in the deposit. The organic content is in the range 5–18%, the higher values to 3 m depth. NaCl content increases almost linearly with depth, from 7 g/l at 1 m depth to 24–26 g/l at 6 m depth. Kaolinite is predominant throughout the profile, increasing almost linearly with depth. However, smectite has almost the same percentage until 3.5 m depth. The plasticity index varies in the range 60–170% and may be directly related to the clay minerals. Go values decrease with depth, from 14–28 MPa to 1 MPa at 3 m depth, then increase with depth, reaching 5 MPa at the bottom of the very soft material. Vane test results indicated two regions of su versus depth, the first from 1 m to 5 m depth, with su in the range 8–12 kPa, the second from 6 m to 8 m depth, with su in the range 16–18 kPa. There is a trend of linear increase in sensitivity with depth, from 4.5 at 1 m depth to 7–9 at 7 m depth. Salt content does not seem to play a major role in the sensitivity of Sarapuí II clay.