Preliminary Geotechnical Properties Northeast Central Pacific Nodule Mining Area

Thirteen short cores raised from water depths of 4.2 to 4.5 km in the Deepsea Ventures, Inc., mining claim area during Phase 1 of the NOAA Deep Ocean Mining Environmental Study (DOMES) were geotechnically analyzed at Lehigh University in 1975-76. The sediments are predominantly fine-grained, cohesive siliceous pelagic clays having average specific gravities of about 2.3. Selected geotechnical properties, measured and averaged over the 188 to 438 mm length of the cores, are: bulk density, 1.32 Mg/m³; water contents 178% dry weight; liquid limit, 137%; plastic limit, 82%; vane shear strength, 5 kPa; and sensitivity, 3.6. Reported shear strength and sensitivity values may be slightly lower because of sample disturbance. The data reported in this investigation are similar in magnitude to data for pelagic clay and siliceous ooze previously reported in the literature.