Geology Reference
In-Depth Information
description to a few coded classi
cations, as in industry standards, is
over-simplistic but it is a
fine balance between providing too much
geological information and too little.
Generally, GI loggers tend to provide minimal summary descrip-
tions, as per the examples given in BS5930 and other standards, and
avoid commenting on unusual features, although it varies from com-
pany to company and, of course, the knowledge and insight of the
logger. Some guidance on standard logging is given in Appendix C and
examples of borehole logs are provided in Appendix D and discussed
later. Fletcher (2004) provides many examples of the kind of geological
information that can be obtained from logging of cores for engineering
projects, most of which would be missed if following standard guide-
lines for engineering description and classi
cation.
There is much to be said for the engineer informing the GI contractor
of his preliminary ideas regarding the ground model, based on desk
study and reconnaissance, so that the contractor knows what to look
for and can update the model as information is gained.
Rock exposures are particularly important for characterising fracture
networks. Orientations are usually measured using a compass clin-
ometer, as illustrated in Figure 4.17, with different diameter plates
used to help characterise the variable roughness at different scales
(Fecker & Rengers, 1971). Electronic compass/clinometers are under
Figure 4.17 Joint
survey underway
using Clar compass
clinometer attached
to aluminium
plates.
Investigation for
Glensanda Super
Quarry, Scotland.
 
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