The resistivity values of the different soils are listed in table 1.4
Material
Resistivity ( -cm)
Massive rock
> 400
Shale and clay
1.0
Seawater
0.3
Wet to moist clayey soils
1.5 - 3.0
Table 1.4 : Resistivity of different materials
Procedure
The set up for the test is given in figure 1.13. In this method, the electrodes are driven approximately 20cms in to the ground and a dc or a very low frequency ac current of known magnitude is passed between the outer (current) electrodes, thereby producing within the soil an electrical field and the boundary conditions. The electrical potential at point C is Vc and at point D is V d which is measured by means of the inner (potential) electrodes respectively.
---------(1.1.1)
---------(1.1.2 )
where,
is resistivity,
I is current,
, , and are the distances between the various electrodes as shown in fig. 1.13.
-cm) 
is resistivity, 
, 
, 
and 
are the distances between the various electrodes as shown in fig. 1.13. 
