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If the stereotomographic technique was used only to lump a given
information for the entire mine, that would be of little significance. However,
this is not the case because it is possible, in the RQD example case, to
delimit the domains locally by reducing the sampling, and also to discriminate
between the low and the high RQD isovalues. Consequently, it will
be possible to know the pattern or the attitude, if any, of the main
discontinuities. Indeed, two things can be done to increase the resolution or
the contrast of the figures while another device can be used to improve their
quality. Increasing the number of classes for RQD intersections or using a
grid mesh smaller than the original one would be sufficient to discriminate
adequately between weak and strong qualities of rock. To improve the
quality of the drawings, it would be necessary to reduce the core intervals
of paired boreholes before doing any informatic treatment of data. As stated
in a previous section, the reduction of core intervals will increase the
definition of the smallest details in the case of large scales, whereas an
increase of such intervals will bring about a reduction in the ability to see
the details but at the same time enhance the possibility to delimit the large
regional structures present in small scales. The following ratios may be useful
to serve our needs:
δ = 153.049/(n^0.5) = 56.628/φ = 3.146/ε
where "δ" = mean definition based upon the number of characters (2.54 mm
x 4.23 mm) met along the radius of reference orthogonal axes of the net
(in degrees), "n" = number of characters used in the net, "φ" = diameter of
the net used (in cm), "ε" = enlargement required (in multiples of a
reference net having an 18-cm diameter).
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The following practical example will serve to illustrate the procedure
used to increase both the resolution and the quality of figures discussed.
From a preliminary study that has been published in Spanish (Labossière,
1982), three main families of discontinuities were abstracted, discontinuities
that could be related to the presence of a monzonitic dyke or of skarn
zones. The respective attitude of such discontinuities is given by the following
azimuths and dips: N105/80, N166/52, and N046/47.
On Fig. 3, which represents the stereotomogram of Fig. 1, one can see the
cyclographic traces of the three discontinuities, whereas on Fig. 4 the
corresponding histomogram is shown. At this point, however, it must be said
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page-9
