Submersible mountedin situ geotechnical instrumentation

Abstract

A series of new miniaturized in situ geotechnical instruments were developed and subsequently field tested with the Deep Sea Research Vessel (DSRV) Alvin during October of 1980 in various sedimentary features on the U.S. East Coast continental slope and upper rise within the Wilmington Geotechnical Corridor. These instruments are herein described and include a cone penetrometer, resistivity/conductivity probe, miniature in situ soils testing system has not been attempted previously from a submersible, primarily because of the expense and general unavailability of a suitable vehicle.The geotechnical instrument system used with the Alvin was designed to collect in situ shear strength (cone resistance), porosity, wet bulk density, pore pressure (including induced insertion pressure and its dissipation rates) and seafloor gradient data. The coring system was intended to ground truth the piezometer, an inclinometer and a small diameter coring system. The various drive systems, controls and data recording systems in situ measurements by laboratory testing and to obtain a soil are also briefly discussed, sample for further testing such as size analysis and Atterberg limits.

Seabed geotechnical parameters from electrical conductivity measurements

“…The four-electrode probes rely upon direct contact with the sedi- merit and may be smaller than the 5-cm hand-held probe used in the laboratory studies, discussed above, of intermediate size such as the submersible-mounted probe discussed by Lambert [14], or the in-situ probe for use in unconsolidated, coarsegrained sediments shown in Figure 2, or may consist of four conductors spaced far apart for large area mapping. Inductive probes, which do not require physical contact with the sediment but instead generate an electromagnetic field and detect the resulting secondary field, are more complex.…”

Generic assessment of steep-slope seabed environments; identification of sediment cover and evaluation of swath sonar systems for OTEC site mapping

“…What are applicable to more regional surveys for evaluation of OTEC development are a series of inexpensive in-situ sampling devices that can be deployed from manned submersibles or remotely operated vehicles such as ARGO/JASON or a series of vehicles built by Ametek, Straza Division. Instruments such as gamma probes, static cone penetrometers, piezometers, vane shear, and push-sample corers are available off-the-shelf (Perlow and Richards, 1972;Lambert, 1982;Prindle and others, 1983).…”