6.5.2.2 Determining the soil resistivity with the Wenner method

The Wenner method is a widely used technique for measuring earth resistivity. Figure 6.5.2.2.1 shows the arrangement of the measuring probes for this measuring method. The measurement is carried out from a centre point 'M' (e.g. intended insertion point for an earth rod), which is retained for all subsequent measurements. Four measuring probes (earth spikes 30 to 50 cm long) are inserted into the ground at intervals of 'a' on a marked-out route and connected to the earth measuring device. The drive-in depth of the measuring probes should not exceed 1/20 of the distance 'a'.

The earth resistivity of the soil under investigation is determined from the measured resistance 'R' (Equation 6.5.2.2.1):