Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Development and application of modern geophysical techniques (including radar) to the exploration and exploitation of ornamental stones

New techniques are available to the ornamental stone industry and their application will play an important role to the increase of productivity. The areas of engagement are:
Prospecting for new quarries to be developed in the future and in operating quarries, to the evaluation of the rock mass under exploitation.

New products resulting from the project are:
Development of a sophisticated processing and interpretation radar software which enables the 3-dimensional representation of the fracturation system.
A new borehole antenna with superior characteristics to those available in the market in terms of the operational frequency.
Familiarisation with all existing measuring acoustic systems and evaluation of their performance with detecting microfractures in marble-granite.
The field procedure and interpretation techniques of the surface GPR borehole GPR tomography, acoustic, resistivity and electromagnetic (VLF) methods were optimised and valuable experience and practical knowledge was gained, after testing and developing the techniques. These have been applied to marble and granite quarries, modified accordingly and their results verified after destructive investigation.

The 3 dimensional detection of fractures in ornamental stone quarries has been tested and validated for resolutions of about a 1 cm with penetration depths of the order of 8 m. Furthermore, it has been manifested that the surface radar is extremely well suited to quarry needs and its capabilities are:
900 MHz: resolution on a centimetre scale and a penetration depth of 5 m, %: 300 MHz: resolution of 10 cm and a penetration depth of up to 12 m.

A high frequency (500-1500 MHz) borehole antenna has been manufactured. This antenna is a worldwide innovation, since no other borehole antenna operates at such a high frequency, the highest frequency available being 120 MHz.
The borehole radar has shown obvious qualities of resolution and suitability to quarry work: it enables visualisation of fractures between boreholes at a required depth. Whereas the non-destructive surface radar possesses qualities adapted to a work face, the borehole radar can be used to estimate the value of an unexposed zone. The surface radar is very disappointing in such conditions because this technique is not capable of penetrating the weathered zone. High resolution tomography, however, can be used to estimate the degree of fracturing in the surrounding 10 m.

Currently, only the 2 dimensional tomography software is able to restore an image of the fractures. The 3 dimensional reflection tomography is also being tested.


Jean-Christophe GOURRY, (Engineer)
Tél.: +33-38643968
Fax: +33-38643361