Soil Resistivity Testing In Winter Season??? 1

[ThePunisher]

I would like ask if it is possible to conduct 4 point Wenner method soil resistivity testing during Winter Season when the soil is frozen. Is this testing possible during Winter?

 

[tinfoil]

The TESTING can be done.

The difficulty is in correlating the <0°C results of frozen soils with the 'warm' results.
From what I understand, frozen soil resistivity can vary by a factor of 50 to 100 from 'wet' soil.
I am not aware of any industry-accepted way to relate the two.

 

[waross]

www.aemc.com,[/URL] Understanding Soil Resistivity Testing] Bear in mind that these results are based on homogeneous conditions that won’t necessarily exist at the site.

With frozen soil and based on 6" electrode depth,there are two possible considerations;
1; The frost line is below the entire ground grid. In this case the conditions may be considered homogeneous and the resuts may be accurate. More electrodes or deeper electrodes may be required to meet your specs.
2; Part or all of the ground grid may be below the frost line in unfrozen soil. With the test electrodes in frozen soil and at least part of the ground grid in unfrozen soil, the test results will probably be erroneous. Consider either installing the test electrodes deep enough to be in unfrozen soil or consider a different test method.
I once worked on a project to determine the moisture content of lumber in a dry kiln. The two methods in use were:
1; Resistance. Two pins were driven into a board and the resistance was measured. There was a good correlation between the resistivity and the moisture content.
2; Capacitance. Water has a very high capacitive index and the measured capacity formed by placing an electrode a known distance above the ground in the lumber stack (about four feet above the ground) had a good correlation to the water content of the lumber.
When the lumber was frozen, the resistivity greatly increased and the capacitive index dropped greatly to the point that both methods showed frozen lumber to be zero percent moisture content, regardless of the actual moisture content.
I am sure that you will see parallels here.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[HamburgerHelper]

Some consulting companies will submit bids on a substation using the summer resistivity in designing the grounding grid and in the contract state that winter measurements will be made and any additions will add additional cost. It is so they can lower the dollar value of the bid knowing full well that their preliminary design won't work.