APPLICATION OF THE ELECTROSTATIC QUADRIPOLE TO SOUNDING IN THE HECTOMETRIC DEPTH RANGE

A current is injected with an electrostatic quadripole by electrostati c influence from two poles located above the ground surface. In the ai r, the voltage is also measured, between two other poles. This techniq ue can be used whatever the ground surface and it overcomes the diffic ulties which arise in the DC resistivity method when the contact betwe en the electrodes and the ground is not good enough. The satisfactory results obtained for low investigation depths, one to a few metres, le d us to make an attempt to use this method for greater depths. Among o ther avantages, the method is easy to use on very resistant surfaces ( dry, frozen, uncompacted, etc.) and extends those offered by EM method s.Here, we present comparisons between DC electrical soundings and ele ctrostatic ones in order to establish the practicability of this new t echnique. These comparisons include the presentation of solutions allo wing to overcome technical measurement problems and to interpret the r esults by taking into account the effect of induced currents.