Study of Driven Ground Rods and Four Point Soil Resistivity Tests

A series of tests has been conducted to compare the apparent soil resistivity of a driven ground rod with the soil resistivity measurements obtained by the four point method. Both uniform and non-uniform soil conditions were encountered. A theoretical analysis is performed for the two test methods in two-layer soil conditions. An equation is derived to enable the calculation of the driven rod apparent soil resistivity based on the four point soil resistivity tests.. The actual test results are analyzed based on two-layer theoretical considerations. Possible limitations of the four point test method are discussed.