On the basis of the FEM forward modeling for a point-source on a 2-D structure and with the Sclumberger electrode array featuring large and uneven distributed electrode-spacing considered, a 2D forward modeling has been realized for resistivity/IP sounding of large electrode-spacing by dividing the whole calculation area into 3 zones, i.

Feasibility of dipole equatorial resistivity sounding in tunnel;

Anomalous of large polar distance dipole-dipole resistivity sounding in tunnel;

Inversion of GA and least square for resistivity sounding data;

The 2 D inversion is the best method in the interpretation of DC resistivity sounding profiles data owing to its high speed, but the 3 D inversion, by contrast, needs more measured data and more computer time.

Combining with two practical examples of the prospecting of coal cave , this paper introduces the field word essentials its effect by using the resistivity sounding method to prospect the underground coal cave.

When the resistance difference between the waterbearing formation and the waterless formation is small, the effectiveness is low using the resistivity sounding method, so the reflection coefficient (K) method is used in the explanation of resistivity sounding ρs value.