Geology Reference
In-Depth Information
Figure 4.38
Output from BIPS
down-hole
discontinuity
orientation device,
being used during
logging of rock
core, Taejon
Station, South
Korea.
indicated a completely different style of jointing to those measured
in exposed faces (essentially along horizontal scan lines). The data are
presented in
Figure 4.39
and it can be seen that the borehole data
essentially de
ned a girdle of joints at 90 degrees to the main pole
concentration that was measured from the horizontal scan line data.
Both sets of data were required to provide the correct geological
picture.
Other down-hole tools include resistivity and gamma ray inten-
sity (even in cased holes) which, whilst often useful for oil
exploration and coal mining, generally have rather limited appli-
cation to civil engineering, other than possibly for locating clay-rich
horizons.
Instrumentation is used to establish baseline ground conditions at
a site, most commonly in terms of natural groundwater
uctua-
tions. It is also used to monitor changes at a site brought about by
construction activities such as excavation or blasting. Instrument
systems need to be designed carefully so that they are reliable;
there needs to be built-in redundancy for instruments that may fail
or become damaged by site works or by vandalism. Incoming data
must be readily interpretable if some action is to be taken as a
consequence. Instruments are often used during the works to
check performance against predictions. Displacements and water
levels can be monitored and compared to those anticipated. First
(ALERT) and second (ALARM) level trigger conditions can be
de
nedwithprescribedactionplans.Datacanbesentremotely
to mobile phones or by email to engineers who have the respon-
sibility for safety and the power to take action such as closing a
road or evacuating a site. Other instruments that might be
