Geology Reference
In-Depth Information
Figure 4.41 Halcrow buckets retrieved at Yee King Road landslide investigation (Hencher
et al., 2008). These are unusual in that they contain sediments (from turbulent
ows down the
the water has risen in the borehole between inspections. Left side bucket is attached by
fishing
line to lead weights used to lower the buckets down the borehole.
information by telemetric systems. Other instruments include
pneumatic or vibrating wire piezometers that respond very quickly
to changes in pressure (
Figure 4.42).
Because they require almost
no water
flow to record change of pressure (unlike a standpipe),
they can be grouted in place in the borehole and several instru-
ments can be installed in the same hole, which can save cost
(Vaughan, 1969; Mikkelsen & Green, 2003).
Instruments that are used to measure displacement include
strain gauges, tilt meters, inclinometers and extensometers.
They can be mechanical or electrical, for example, using vibrating
wire technology.
Figure 4.43
shows the end of an extensometer
anchored deep behind the working face of a large copper mine in
Spain and
fitted with lights and a claxon horn to give warning if
