TDI-Brooks Incorporates FIELAX GMBH's Electronics & Thermistor String

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.