Geology Reference
In-Depth Information
form the basis for planning any necessary ground investigation. The
preliminary model should allow an initial layout of the components of
the project and, for buildings, some insight into the types of foundation
that might be required. For tunnels, decisions can be made on locations
for portals and access shafts. The degree to which walk-over studies and
field mapping can be cost-effective is often overlooked, as illustrated by
a case example in Box 4-6.
Box 4-6 Case example: cost-effectiveness of site
reconnaissance
-
bridge abutment, Lake District, UK
The
first ground investigation that the author was involved with was for a bridge abutment in the Lake
District, UK . Figure B4-6.1 is a view of the rock cliff that was to form the abutment, and halfway down the
cliff is a platform. Figure B4-6.2 is a side view of the platform. The man in the middle of the photograph is
logging a borehole, using a periscope that has been inserted into a hole, inclined at about 45 degrees,
drilled into the rock from the same platform. In the foreground, rock can be seen with a fabric dipping
roughly parallel to the cliff. For reasons that are unimportant now, a question arose regarding the
geological structure being logged by the periscope.
The site engineer was asked for his geological map of the rock along the river (including the 100%
exposed cliff). He replied,
'
what map?
'
Figure B4-6.1 Drilling platform on cliff.
 
 
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