|
Section 4: Rock mass assessment |
Regional Geophysics Group, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
There is an increasing need to map and understand rock fracture networks in order, for instance, to predict the spread of contaminants in the sub-surface, to optimize borehole siting in aquifers whose storage results from fracturing, and for civil engineering applications. The use of azimuthal resistivity and seismic measurements for the determination of concealed sub-vertical fracture orientations has been previously reported but to date the methods have found little generalapplication.
The results of resistivity and seismic azimuthal measurements on chalk and limestone at several sites in southern and eastern England are reported. A number of distinct preferred azimuths are apparent in the data and the two independent techniques give generally consistent results. The geophysical indications are assessed relative to outcrop measurements of fracture and joint azimuths and conclusions are drawn on the persistence of fracture sets both laterally and vertically.
