Environmental Engineering Reference
In-Depth Information
Installation
Geophones can be installed at shallow depths below the surface, cemented into boreholes,
or mounted on a rock face in an excavation as shown in Figure 4.24. The best results for
rock studies are obtained when the transducer is located in the rock mass.
Case Studies
Cut-Slope Failure (Koerner et al., 1978)
Operations : The toe excavation of a large fill was monitored by an acoustic emissions
device. Five cuts were required to cause failure over a 21-day period. After each cut, the
T
JB
JB
Geophone
spike
3 in.
Hole
filled
1 3 ft
T
(a)
(b)
JB
JB
Cased
section
Sand
filled
Open
section
100
300 ft
10 25 ft
T
Probe
Concrete
(c)
(d)
FIGURE 4.24
Types of microseismic transducer mounting techniques: (a) surface mounting; (b) shallow burial; (c) deep
burial; (d) borehole probe. (From Hardy, H. R., Jr. and Mowrey, G. L., Proceedings of the 4th International
Conference , Zurich, April, A. A. Balkema, Rotterdam, pp. 75-72. With permission.)
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