Related Experiment Video
Updated: Sep 4, 2025
10:27
A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System
Published on: June 12, 2019
8.8K
Moderate Cover Bleeder Entry and Standing Support Performance in a Longwall Mine: a Case Study
Mark Alexander Van Dyke1, Ted M Klemetti1, Ihsan Berk Tulu2
1Ground Control Branch, CDC NIOSH, Pittsburgh Mining Research Division, Pittsburgh, PA 15236, USA.
Mining, Metallurgy & Exploration
|July 15, 2022
Summary
Bleeder entries in longwall mining require robust standing supports to remain open for ventilation. Research shows support loading and convergence increase with proximity to the gob, while roof sag is independent.
Area of Science:
- Mining Engineering
- Geotechnical Engineering
- Occupational Safety
Background:
- Bleeder entries are crucial for longwall mining operations, facilitating personnel and supply movement and diluting mine air contaminants.
- These entries require long-term stability for continuous ventilation, necessitating effective support systems.
- Previous research has not fully detailed the long-term performance of standing supports in bleeder entries under varying mining conditions.
Purpose of the Study:
- To investigate the long-term performance and stability of standing supports in moderate cover bleeder entries.
- To analyze the influence of longwall mining activities and aging on support loads, roof convergence, and pillar stresses.
- To provide data for optimizing bleeder entry design and support strategies in longwall mining.
Main Methods:
- Field instrumentation including borehole pressure cells (BPCs), standing support load cells, convergence meters, and roof extensometers.
- Numerical modeling to simulate stress distribution and deformation around bleeder entries.
- Visual observations of the bleeder entries over an extended period (over 1.5 years).
Main Results:
- Standing supports closer to the longwall gob experienced the highest loads and convergence.
- Roof sag was largely independent of proximity to the gob.
- Borehole pressure cell readings were influenced by both gob proximity and pillar depth, indicating complex stress interactions.
Conclusions:
- The study demonstrated that bleeder entry roof behavior can be independent of pillar and standing support loading.
- Rear abutment stress on the studied bleeder entry design was minimal.
- Increased proximity of mine development, pillars, or supports to the gob directly correlates with greater applied load due to rear abutment stress.
