What does the average soil resistivity relate to in the Wenner Four-Pin Method?

The average soil resistivity in the Wenner Four-Pin Method is determined by measuring the voltage drop between the center pair of pins while a known electric current is flowing between the two outer pins. This technique specifically calculates the resistivity by applying a constant current into the ground and measuring the resultant voltage across the inner pins.

In this method, the resistivity can be calculated using the formula:

[ ρ = \frac{2\pi aV}{I} ]

where ( ρ ) is the resistivity, ( a ) is the spacing between the pins, ( V ) is the measured voltage drop across the inner pins, and ( I ) is the current injected through the outer pins. This relationship is foundational for soil resistivity testing, as it provides meaningful data regarding the electrical characteristics of the soil, critical for designing cathodic protection systems.

Other options refer to related concepts but do not accurately define how average soil resistivity is calculated in the context of the Wenner method. For instance, while the voltage drop and electric current are part of the process, the specific focus on the center pins and their measured voltage drop as a direct function of the current from the outer pins is what explicitly connects to