UFC 3-570-06
JANUARY 31 2003
Figure 7-27. Two-Pin Method ("Shepard's Canes") of Soil Resistivity Measurement
INSTRUMENT
D
Augered
Depth as
Holes
Desired
(if required)
to 3 ft.
D = ONE FOOT PIN SPACING
7-11.3
Other Methods (Soil Rod, Soil Box). A soil rod is essentially a two-pin
resistivity-measuring device where the electrodes are both mounted on a single rod, as
shown in Figure 7-28. As in the other two-pin method, the resistivity of the soil to a very
shallow depth is measured. Also, the soil must be soft enough to allow penetration of the
rod. Measurements using the soil rod, however, can be taken quickly when measuring in
soft soil.
Figure 7-28. Soil Resistivity Measurement Using a Soil Rod
Contact Ter mina ls to
AC Resistance M ea sur ing
Instrum en t
Te rm ina l, con nec ted by wire
Te rm ina l, con nec ted
(ins id e sha nk) t o me ta l tip
to m e tal tip
1/2 inch Round Steel Shank
M etal T ip, in sulate d
from Rod Shank
7-11.3.1 When it is impractical to make field measurements of soil resistivity, soil
samples can be taken and the resistivity of the sample can be determined by using a soil
box. As shown in Figure 7-29, the method of measurement is essentially the four-pin
method. Metal contacts in each end of the box pass current through the sample.
7-44
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