10
3. The integrity of the coal pillar ribs in the active
mining zone is maintained for at least the initial
24 in.
4. The stability factor for pillars in the active mining
zone is greater than 1.3.
5. Good roof caving during the retreat of pillars
helped reduce stress transfer to the active mining
zone.
6. In the active mining zone, there is a slight roof
convergence of 0.1 in. Additionally, the front abut-
ment load is minimal, and there is a small rib hori-
zontal displacement of about 0.04 in.
The findings from this case study and others are cur-
rently used by MST researchers to calibrate a numerical
model that simulates rib brows in underground coal mines.
This calibrated model will serve as the foundation for con-
ducting a parametric study aimed at answering three criti-
cal questions for coal mine operators:
1. What geological, geometrical, and loading factors
contribute to the formation of rib brows? Factors
may include the strength of the rock parting and
coal seam, the thickness of the rock parting and
coal seam, overburden depth, and others.
2. How to eliminate or reduce the formation of rib
brows?
3. How to assess the stability of formed rib brows?
4. What are the most effective support methods for
stabilizing rib brows?
SUMMARY
The current study on rib monitoring was conducted in a
room-and-pillar panel where the rib consists of a rock layer
overlying a coal seam, making it susceptible to rib brow
formation. This study evaluated the potential for rib brow
formation during the development and pillar retreat load-
ing phases.
The installation of instruments in pillar P3 began while
the continuous miner was advancing one break inby the
instrumented pillar. Monitoring continued for approxi-
mately 6 months until half of the instrumented pillar was
mined. The instrumentation layout includes RXs, LCs,
BPCs, and MPBXs installed on both the entry side and the
cross-cut side of the instrumented pillar. Short encapsula-
tion pull-out tests were conducted to evaluate the anchor-
age capacity of the rib bolts installed in coal seam and shale
rock.
The absence of rib brow formation at the instrumented
pillar is due to several factors. A strong, thin rock parting,
with a compressive strength of 5,556 psi and supported by
Figure 19. Measured rib displacement in the instrumented
pillar
3. The integrity of the coal pillar ribs in the active
mining zone is maintained for at least the initial
24 in.
4. The stability factor for pillars in the active mining
zone is greater than 1.3.
5. Good roof caving during the retreat of pillars
helped reduce stress transfer to the active mining
zone.
6. In the active mining zone, there is a slight roof
convergence of 0.1 in. Additionally, the front abut-
ment load is minimal, and there is a small rib hori-
zontal displacement of about 0.04 in.
The findings from this case study and others are cur-
rently used by MST researchers to calibrate a numerical
model that simulates rib brows in underground coal mines.
This calibrated model will serve as the foundation for con-
ducting a parametric study aimed at answering three criti-
cal questions for coal mine operators:
1. What geological, geometrical, and loading factors
contribute to the formation of rib brows? Factors
may include the strength of the rock parting and
coal seam, the thickness of the rock parting and
coal seam, overburden depth, and others.
2. How to eliminate or reduce the formation of rib
brows?
3. How to assess the stability of formed rib brows?
4. What are the most effective support methods for
stabilizing rib brows?
SUMMARY
The current study on rib monitoring was conducted in a
room-and-pillar panel where the rib consists of a rock layer
overlying a coal seam, making it susceptible to rib brow
formation. This study evaluated the potential for rib brow
formation during the development and pillar retreat load-
ing phases.
The installation of instruments in pillar P3 began while
the continuous miner was advancing one break inby the
instrumented pillar. Monitoring continued for approxi-
mately 6 months until half of the instrumented pillar was
mined. The instrumentation layout includes RXs, LCs,
BPCs, and MPBXs installed on both the entry side and the
cross-cut side of the instrumented pillar. Short encapsula-
tion pull-out tests were conducted to evaluate the anchor-
age capacity of the rib bolts installed in coal seam and shale
rock.
The absence of rib brow formation at the instrumented
pillar is due to several factors. A strong, thin rock parting,
with a compressive strength of 5,556 psi and supported by
Figure 19. Measured rib displacement in the instrumented
pillar