Environmental Engineering Reference
In-Depth Information
Intact rock signature
I - 10
×
10
2
*
Caved rock signature
I - 5
×
10
3
*
6 - 35
×
10
3
*
Void signature
* Typical response ranges in ohms
Lateral distance (f t)
FIGURE 2.33
Results of electrical resistivity study for coal mine using pole-dipole method. (Courtesy of Woodward-Clyde
Consultants.)
Limitations
Since resistivity is a function of water content and soluble salts, materials with widely dif-
fering engineering properties can have the same resistivity. Therefore, correlations from
one location to another may not be possible. Differentiation between strata may not be
possible where the overlying material has an extremely high resistance.
Water-table location often limits the depth for practical study because conductivity rises
sharply in saturated materials and makes differentiation between horizons impossible.
