Analysed Ranges and Auxiliary Curves for Analysis of ρ-a Curves Obtained with Wenner's Four Electrodes Arrangement

Abstract

For the design of a grounding electrode, the ground configuration at an intended site for the electrode needs to be clear. For this purpose, in many cases, a ρ-a curve from the measured results with Wenner's four electrodes arrangement is analysed by Sundberg's standard curves and Hummel's auxiliary curves. This paper is concerned with the analysis of the ρ-a curve for three-layer ground.
First, for deduction of three parameters of ρ₁, h₁, and ρ₂, the best analysed range of ρ-a curves is searched from many model data, and it is found that the best range is from the beginning point to 0.8 L_i1, , where L_i1 is the value of a at the first inflection point of the ρ-a curve. Next, for deduction of two parameters of h₂ and ρ₃, usual Hummel's and other four auxiliary curves are descussed from the view point of two layers displace-ment to one layer. For deduction of ρ₃, usual Hummel's curves are good enough for all types of ρ-a curves. But, for deduction of h₂, it is pointed out that, series-displacement curves are excellent for UD-type of ρ-a curves and Ono-displacement curves for DD-type, meanwhile usual Hummel's curves are good enough for DU-and UU-type. Then the best analysed range for deduction of h₂ and ρ₃ is also searched, and it is found that the best range is estimated from L_i1 or L_i2, where L_i2 is the value of a at the second inflection point of the ρ-a curve.