Environmental Engineering Reference
In-Depth Information
I
V
A
M
N
B
o
s
(a)
Schlumberger array
I
V
A
M
N
B
o
o
o
(b)
Wenner array
a
na
a
I
V
Dipole
−
dipole array
(c)
AB source dipoles, MN receiving dipoles
FIGURE 2.32
Electrode (array) configurations for resistivity measurements. (From ASCE
Technical Engineering and Design
Guides,
adapted from the U.S. Army Corps of Engineers, 1998.)
Underground Coal Mine Study
A colleague advised the author of a study of an underground coal mine, where an expert
in electrical resistivity used a “pole-dipole” method. Three different signatures were
obtained, as shown in
Figure 2.33:
intact rock, caved rock, and voids. The signatures, ini-
tially considered as anomalies, were confirmed by core borings and comparisons with old
mine maps.
Railway Tunnel Through Poor Quality Rock
Dahlin et al. (1996) report on a resistivity investigation for a railway tunnel in Sweden. The
imaging system consisted of a resistivity meter, a relay-matrix switching unit, four elec-
trode cables, a computer, steel electrodes, and various connectors. The total length of
investigation was of the order of 8200 m to depths of 120 m. Color-coded results showed
variation in rock quality along the entire proposed alignment. Low resistivities indicated
very poor rock. Core borings confirmed the interpretations.
