TDI-Brooks has successfully married their 6-m long pneumatic vibracorer (pVC) with FIELAX GmbH’s electronics and thermistor string to achieve in situ thermal resistivity testing (TRT) at several offshore wind turbine cable sites in the New York Bight lease areas (see Figures 1 and 2). The pneumatic vibracorer (pVC) typically provides greater penetration in these sandy/gravely seabeds than do the electric vibracorers (VCs).

One of the learnings from the test was the need to limit penetration times, optimally to less than 5 minutes to facilitate ease of data interpretation.  At most sites, up to twenty (20) individual thermal response tests (TRT) measurements were made down the thermistor string after burial into the seafloor (see Figure 3).

The thermistor string attached with outriggers to the VC barrel was left in the seafloor for 20-minutes to log the dissipation of frictional heat from insertion. The thermistor string then was given a 10-sec heat pulse and left another 20-minutes in the seafloor to measure the soil’s thermal resistivity at each individual thermistor, which were spaced at 0.25 m intervals down the string. FIELAX used proprietary software to calculate TRT values.


Figure 1. Schematic of the sensor string for thermal measurements.

Figure 2.  pVC with VibroHeat electronics and thermistor outrigger add-on (upper), Thermistor outrigger attached to the VC barrel (left),TRT electronics and battery pack (right).

Figure 3.  Example of temperature of each sensor while in the seabed (upper panel); and TRT results (lower panel).


More details on our TDI-Brooks HERE.

Contact Jim Brooks at / +1 979-693-3446 and/or Melissa Wood at / +1 713-208-1734

About TDI-Brooks

TDI-Brooks is a 25-year old research and service company specializing in geotechnical and offshore survey projects; multi-disciplinary oceanographic and environmental projects; surface geochemical exploration; and high-end environmental chemistry for IOC and OSWF clients along federal and state agencies. TDI-Brooks acquires, processes and interprets geological, geophysical and geotechnical data to assist in assessing the suitability of offshore sites for wind farms and their infrastructure. We have extensive experience, providing detailed analyses of the seabed and accurate assessments of subsurface conditions for offshore windfarm sites.

Contact Us

TDI-Brooks International, Inc.
14391 S. Dowling Road
College Station, TX 77845

Phone: +1 (979) 693-3446