9. Drilling radar in reflection mode

9.1 Scope and conditions of application

• Geological radar, used in reflection mode from a borehole, explores the terrain around the borehole within a radius ranging from a few meters to several dozen meters, depending on the weathering properties of the materials. In a crystalline environment or homogeneous limestone massif, it can be used to detect fractures and cavities (e.g. karsts).

• The electromagnetic wave must be able to propagate; in highly electrically conductive materials, geological radar is therefore not indicated. The resistivity of the ground is generally considered to be greater than 100 Ω · m (for a radius of investigation greater than 3 m).

  If the borehole is cased,...