As part of the thermal survey, Geotherm can conduct laboratory testing on samples of native soil material collected from the proposed cable route.
A varying degree of sample types can be tested, from a simple bag of material, to most sizes of undisturbed push tubes. Testing of rock core samples can also be undertaken in the laboratory.
Thermal resistivity testing is done to determine the fully dry thermal characteristics. In addition, samples collected from each site can be progressively dried and tested across a range of moisture contents to develop the TR versus moisture content relationship graph, know as a “dry-out” curve. This curve is of particular use if the native soil around a cable partially dries out under cable operating temperatures, and determines the critical moisture content often used for cable ratings. Geotherm will also determine the moisture content of each sample and the dry density.
Geotherm also test various quarry products to determine their thermal suitability as cable backfill/bedding. Various methods of testing soil for engineering purposes are used to allow accurate sample preparation for thermal resistivity testing. In addition, samples can be prepared to customer requirements.
Laboratory testing also includes flowable and concrete type backfill/bedding materials for power cables. Geotherm specialise in the design of such materials. See Design of Cable Backfill.