Soil Resistivity Testing 10 Common Mistakes
This is a series of short posts on Soil Resistivity Testing and the common mistakes encountered, with practical advice on how to avoid Soil Resistivity Testing 10 Common Mistakes.
Soil Resistivity Testing Buried Interference can occur when, bare metallic structures (including concrete-encased metal) of significant length buried in the vicinity of the measurement traverse can distort Soil Resistivity Testing results.
When a measurement traverse runs parallel to a long structure of this type, significant error begins when the clearance between the traverse and the structure is on the same order as the electrode spacing. The error increases as the electrode spacing increases compared with the clearance.
A similar effect is observed when the electrodes are placed near relatively small grounding systems which are interconnected by means of overhead wires. As a rule of thumb, to avoid significant error, there should be no bare metallic structures of significant size buried within a radius r of any of the measurement electrodes, where r is the spacing between adjacent current and potential electrodes.
When the measurement traverse runs perpendicular to a buried metallic structure without crossing it, the clearance requirement need not be as severe. Computer modelling of the buried structure and measurement electrodes can provide an estimate of the measurement error to be expected for different soil structure types.