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Underground
coal mining
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Operation
An installation of permanent surface and temporary
underground seismometers communicates with a seismic
controller located on surface for real-time seismic monitoring
of the rock mass. The integrated GPS timing module is used so that
recorded seismic data may be integrated with seismic data from another
nearby system for information about regional seismic events. Any
GS data acquisition
units on the surface use internal GPS modules to ensure common
time with the seismic controller and thus the underground seismic
network. The intrinsically safe GSi units can be used in the potentially
explosive underground environment. These units use a 2-pair cable
for communication and power from a safe area.
Communications
Digital radios are used for communication between
GS stations and the central site. From the mining offices or safe
area underground two twisted-pair copper cables pass through standard
intrinsic safety barriers to service the underground GSi stations.
Up to three GSi stations may use the same comms and power cables,
provided these cables are not more than 2400m in length.
Power
The low power consumption of the GS (less than
1W/channel) allows use of an inexpensive solar panel and battery
unit. The solar power together with digital radio communications
means that the seismic station may be located in places that cannot
be linked to the seismic
controller by fibre-optic or copper cables. The underground
GSi stations use less than 120 mW each, and are supplied with power
from the surface.
Seismic Sensors
Each GS data acquisition unit can monitor and
pre-process up to six seismic signals, in any combination of uni-,
bi- or tri-axial seismic
sensors. For each seismic channel up to 3 logical
channels may be extracted with GS technology. Both geophones
and accelerometers (piezoelectric and Force-Balance) are currently
supported. The GSi units monitor up to 3 seismic signals from a
single tri-axial or three uni-axial geophones.
Seismic Data Processing & Interpretation
The seismograms of every seismic event that triggers
multiple stations are transmitted to the seismic
controller and recorded on a user-specific computer on the Local
Area Network (LAN). The seismic event is automatically processed
and seismic source parameters including the location, time, radiated
seismic energy and co-seismic inelastic deformation are automatically
calculated. This data is confirmed later by manual processing with
the software packages JMTS running
on either Microsoft Windows or Linux computer. Spatial and temporal
trends made then be detected and analyzed using the interpretation
package Jdi. If preferred, seismic
data can be processed off-site by ISSI, and the processed data uploaded
back to the mine afterwards (<5 min turnaround time). ISSI also
offers routine analysis and reporting
services.
This page last updated: January
2007
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