Thermal Resistivity Testing

by Elizabeth Withington 31/01/2017 filed under Laboratory Services


The geotechnical testing laboratory at Geotechnical Engineering can now offer the laboratory measurement of thermal resistivity and conductivity. This measurement is used in the design of underground electrical cables. Electrical cables generate heat and knowing the ability of the surrounding soil to conduct that heat is important when assessing the cable protection required and their operating life.


The main standard for this test that we have adopted is the American Standard – ISRM D5334-14. We can also undertake testing to the other listed standard IEEE 442 – 1981. Both standards originate from America – there is no European equivalent.  There are slight variations in test method that the lab will need to know in advance:  the ISRM method requires the sample to be heated for 60 seconds with readings being taken 20 to 30 times during the test; whilst the IEEE method requires the temperature to be recorded every 15 seconds for 10 minutes.


The test can be carried out on undisturbed and dynamic samples – the test specimen needs to be a minimum of 200mm long and at least 50mm in diameter. 


The test can also be carried out on recompacted samples. Recompacted tests will require compaction to a specific density/moisture content.  The client should inform of such requirements and there will be a cost associated with this recompaction.


The thermal resistivity and conductivity test includes for the determination of moisture content and the calculation of bulk density.


Variations on the test include measuring the thermal resistivity of a sample at received moisture content, fully saturated and fully dried.   Prices should be confirmed with the lab manager prior to testing on 01452 527743 or .

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