ICGCM Papers:
Ground Control Monitoring Systems and Practices
 
 
A Liquid Settlement System for Measuring Roof Sag During Development Mining - A Comparison Between Place Change Mining and a Miner–Bolter
33rd International Conference on Ground Control in Mining
A Liquid Settlement System for Measuring Roof Sag During Development Mining - A Comparison Between Place Change Mining and a Miner–Bolter
by
Andy L Shaffer, Agapito Associates Inc., Grand Junction, United StatesJames D Pile, BHP Billiton, Waterflow, United States
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[Conference] 33rd International Conference on Ground Control in Mining
[Price] Free  [Comments] 0
[Topical Area] Ground Control Monitoring Systems and Practices
[Author] Andy L Shaffer, Agapito Associates Inc., Grand Junction, United StatesJames D Pile, BHP Billiton, Waterflow, United States
[Abstract] 
Key Conclusions:
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The MIDAS datalogger combined with the LSS is innovative permissible technology that shows promise for stable, real time measurements of roof sag and other ground responses in coal mines with commercially available, relatively low cost hardware.
Key Findings:
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Roof sag data were collected every 10 seconds during the cut-and-bolt sequences in each of four instrumented entries during the first 24 hours of mining. The LSS provided relatively stable roof sag measurements and the MIDAS data logger reliably collected a high density of data. Results indicate that while the system is capable of providing sag measurements to within fractions of an inch, improved precision will be necessary for effectively distinguishing roof behavior between place-change and on-board miner-bolter cut sequencing.
Objective of the Paper:
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The MIDAS data loggers and the LSS were used to measure and compare the amount of roof sag during place change mining and development using a conventional miner-bolter under the same geologic conditions in adjacent entries.
Problem Statement:
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When compared to place-change mining, the Joy 12ED25 miner-bolter at a western longwall mine has, on average, reduced the amount of “hang time” for an unbolted cut. Extended hang time while the roof is unsupported is thought to be a key factor for effective roof control. Until recently, real time roof sag measurements at the time of mining were not possible in coal mines due to equipment permissibility restrictions. Intrinsically safe miniature data acquisition systems (MIDAS) data loggers are a new development. The combination of MIDAS dataloggers with overflow settlement measurement practices adapted from dam and embankment monitoring (known as “liquid settlement system” [LSS]) was recognized to be a potential advancement of real time roof sag monitoring in coal mines.