5
by NIOSH researchers for the MPBX produced by MDT,
Inc. are summarized in the following:
• Drill borehole of 2” diameter with borehole slop-
ing slightly downward with a length long enough to
accommodate the MPBX with the instrument head
recessed in the hole.
• Ensure the borehole is free of debris prior to install-
ing the MPBX.
• The MPBX ships coiled. Cut required tape to uncoil
MPBX and roll it out along the floor of the entry.
• Before inserting the MPBX in the borehole, ensure
that the safety spring hanger is in place (See Figure 8).
• Slide the MPBX into the borehole until the MPBX
head is about 2” inside the collar of the hole.
• The MPBX head can be held in place using wooden
wedges while the sacrificial grout tube is inserted
3–4’ into the hole along with a breather tube.
• The collar is packed with rags to keep grout from
escaping and ensuring a fully grouted hole.
• Mix grout at a 0.42 to 0.46 water-to-cement ratio to
ensure proper encasement.
• Continue pumping until you can see the grout com-
ing out of the breather tube from the collar of the
borehole.
• Shut the grout pump off, cut the breather tube, kink
it over to keep suction in the borehole. Then proceed
to cut and kink the sacrificial grout tube.
Transitioning from understanding displacement to the
inherent stresses within the rock, it is crucial to recognize
the interconnectedness of these metrics. Rock stress instru-
mentation attempts to measure the forces and pressures
exerted within the mine’s geological formations. Just as dis-
placement instruments measure the movement, rock stress
instrumentation measures the internal pressures that lead
to these displacements.
Geophones
In mining applications, geophones are typically the seismic
sensor of choice due to their affordability, wide bandwidth,
and dependability (Institute of Mine Seismology, n.d.). The
Institute of Mine Seismology (IMS) Model 3G14 14Hz
geophone (see Figure 9) is model currently used by NIOSH
researchers to measure mining induced seismicity in deep
longwall coal mines (Van Dyke et al., 2018).
The Tri-Axial Seismic Sensor is typically installed down
hole from the surface through means of a preexisting coal
bed methane (CBM) well (See Figure 10). After the gas
Figure 7. MDT Inc.’s MPBX unit with labels showing the
location of key components
Figure 8. Safety spring hanger installed in the deepest
anchor
Figure 9. IMS Model 3G14 geophone (after Institute of
Mine Seismology, 2013)
by NIOSH researchers for the MPBX produced by MDT,
Inc. are summarized in the following:
• Drill borehole of 2” diameter with borehole slop-
ing slightly downward with a length long enough to
accommodate the MPBX with the instrument head
recessed in the hole.
• Ensure the borehole is free of debris prior to install-
ing the MPBX.
• The MPBX ships coiled. Cut required tape to uncoil
MPBX and roll it out along the floor of the entry.
• Before inserting the MPBX in the borehole, ensure
that the safety spring hanger is in place (See Figure 8).
• Slide the MPBX into the borehole until the MPBX
head is about 2” inside the collar of the hole.
• The MPBX head can be held in place using wooden
wedges while the sacrificial grout tube is inserted
3–4’ into the hole along with a breather tube.
• The collar is packed with rags to keep grout from
escaping and ensuring a fully grouted hole.
• Mix grout at a 0.42 to 0.46 water-to-cement ratio to
ensure proper encasement.
• Continue pumping until you can see the grout com-
ing out of the breather tube from the collar of the
borehole.
• Shut the grout pump off, cut the breather tube, kink
it over to keep suction in the borehole. Then proceed
to cut and kink the sacrificial grout tube.
Transitioning from understanding displacement to the
inherent stresses within the rock, it is crucial to recognize
the interconnectedness of these metrics. Rock stress instru-
mentation attempts to measure the forces and pressures
exerted within the mine’s geological formations. Just as dis-
placement instruments measure the movement, rock stress
instrumentation measures the internal pressures that lead
to these displacements.
Geophones
In mining applications, geophones are typically the seismic
sensor of choice due to their affordability, wide bandwidth,
and dependability (Institute of Mine Seismology, n.d.). The
Institute of Mine Seismology (IMS) Model 3G14 14Hz
geophone (see Figure 9) is model currently used by NIOSH
researchers to measure mining induced seismicity in deep
longwall coal mines (Van Dyke et al., 2018).
The Tri-Axial Seismic Sensor is typically installed down
hole from the surface through means of a preexisting coal
bed methane (CBM) well (See Figure 10). After the gas
Figure 7. MDT Inc.’s MPBX unit with labels showing the
location of key components
Figure 8. Safety spring hanger installed in the deepest
anchor
Figure 9. IMS Model 3G14 geophone (after Institute of
Mine Seismology, 2013)