Geology Reference
In-Depth Information
such as slope geometry, strength parameters and groundwater condi-
tions can be varied rapidly, allowing sensitivity analysis. Structural
elements such as soil nails and rock bolts can be included in the models.
There are many similar packages available, all of which are veri
ed
and validated against standard mathematical solutions. There is a
danger that the ease of use of such software in sensitivity analysis,
varying a range of likely parameters, can give a misplaced con
dence
that all possible conditions have been dealt with. If the ground model is
seriously wrong, the results will be meaningless.
Other specialist software packages are used for particular design
tasks such as rockfall trajectory analysis, stresses around tunnels, pile
design and groundwater and contaminant migration modelling.
Details of many of these are reviewed at the web page maintained by
Tim Spink:
http://www.ggsd.com.
Most engineering companies also
have in-house spreadsheets (often based on EXCEL) used to solve
common analytical problems.
Engineering geologists on site should keep careful records as works
advance, using daily notebooks. Excavations should be examined,
described and photographed as necessary. It is often useful to take
photographs and use these as the base for overlays on which to record
features such as geological boundaries, strength of materials, disconti-
nuity orientations and style and locations of seepage. Such records
will be very helpful in the case of any future disputes over payment or if
anything goes wrong. Pairs of photographs taken some distance
apart can be used to allow a 3D image to be viewed, and this is
particularly useful where access is dif
cult or hazardous. Where
discontinuities are measured, it is important to record the location. In
tunnels, description proformas are commonly used as a permanent
record, agreed and signed by the contractor and supervisor, as
illustrated in
Figure 6.33.
assumptions
It is fundamentally important that design predictions are checked
during construction. Design is usually based on widely spaced bore-
holes and the interpretation is almost certainly going to be oversimpli-
fied. Often this does not have any major consequence but sometimes it
does so and the engineering geologist on site should be alert to any
indications that the ground model is incorrect or inadequate. Any
changed conditions should be
flagged up quickly to the designers so
that necessary recti
cations can be made.
