3
cutter roof failure (see Figure 2), sporadic roof shearing,
progressive directional roof falls, and immediate roof sepa-
ration and shifting along with sheared bolts (see Figure 3).
This study was conducted at Subtropolis Mine, which
extracts the Vanport Limestone, which is part of the
Allegheny Formation within the Pennsylvanian System.
The limestone ranges in thickness from 16 to 22 ft (4.9
to 6.7 m), with a mining height of approximately 16 ft
(4.9 m) and a roof span between 30 and 40 ft (9.1 and
12.2 m) (Iannacchione et al., 2020).
The primary roof support pattern at this mine consists
of five, 5 ft (1.5 m) long fully grouted combination resin
Figure 2. Cutter failure along the rib resulted in roof fall Figure 3. Broken cable, sheared bolt, and roof bed shifting
due to high horizontal stresses
cutter roof failure (see Figure 2), sporadic roof shearing,
progressive directional roof falls, and immediate roof sepa-
ration and shifting along with sheared bolts (see Figure 3).
This study was conducted at Subtropolis Mine, which
extracts the Vanport Limestone, which is part of the
Allegheny Formation within the Pennsylvanian System.
The limestone ranges in thickness from 16 to 22 ft (4.9
to 6.7 m), with a mining height of approximately 16 ft
(4.9 m) and a roof span between 30 and 40 ft (9.1 and
12.2 m) (Iannacchione et al., 2020).
The primary roof support pattern at this mine consists
of five, 5 ft (1.5 m) long fully grouted combination resin
Figure 2. Cutter failure along the rib resulted in roof fall Figure 3. Broken cable, sheared bolt, and roof bed shifting
due to high horizontal stresses