![Page 1: Analysis of Potential Implications of Observed Load Transfer Distance and Abutment Angle on Longwall Pillar Loading Heather E. Lawson Jeffrey K. Whyatt](https://reader036.vdocuments.pub/reader036/viewer/2022062517/56649e7f5503460f94b83ae1/html5/thumbnails/1.jpg)
Analysis of Potential Implications of Observed Load Transfer Distance and Abutment Angle on Longwall Pillar Loading
Heather E. Lawson
Jeffrey K. Whyatt
Mark K. Larson
![Page 2: Analysis of Potential Implications of Observed Load Transfer Distance and Abutment Angle on Longwall Pillar Loading Heather E. Lawson Jeffrey K. Whyatt](https://reader036.vdocuments.pub/reader036/viewer/2022062517/56649e7f5503460f94b83ae1/html5/thumbnails/2.jpg)
Background• LTD 4x greater than expected at
Elk Creek Mine• β=21° (H (ft)/900)-1.59 at depths
between 900 ft and 2050 ft
Objective: Establish which regional ground characteristics have the most impact on pillar loading
![Page 3: Analysis of Potential Implications of Observed Load Transfer Distance and Abutment Angle on Longwall Pillar Loading Heather E. Lawson Jeffrey K. Whyatt](https://reader036.vdocuments.pub/reader036/viewer/2022062517/56649e7f5503460f94b83ae1/html5/thumbnails/3.jpg)
Background• ALPS pillar loading equations;
simple and useful• R=1-((D-W)/D)3 where D is load
transfer distance
Disclaimer: Substitution into ALPS software is not recommended
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Background• Ls=H2(tanβ)(ϒ/2), when P≥2Htanβ
• Or else, Lss=((HP/2)-(P2/8tanβ))ϒ
Disclaimer: Substitution into ALPS software is not recommended
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Supplemental StudyLaModel Analysis
• Re-examines role of LTD in TG loading
• Indicates that LTD influences TG loading
• Suggests a modified FT
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Case StudiesSensitivity Study•Compares two scenarios:
– Shallow longwall (supercritical loading)
– Deep longwall (subcritical loading)
•Pillar loads compared to “default” and graphed
Case 1-Shallow Mine
Case 2-Deep Mine
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Shallow Case Study Results• LaModel-based LT loading is most sensitive to D,
• LB is next most sensitive
• LH is least sensitive
• Traditional LT is insensitive to changes in D
Degree of sensitivity is dependent on loading condition
Standard value = 208 ft.
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Shallow Case Study Results• Changes in D have little effect on smaller scale• Loading is moderately to very sensitive to small changes in β
Loading is more sensitive to β than to D.
Standard value = 208 ft.
Parameter LH LB LTAbutment angle, β M* 7% M 12% V 21%
Load transfer distance, D S <1% S <1% I 0%
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Deep Case Study Results• LB in Gateroad 1 is most sensitive to changes in D,
• LH (also Gateroad 1) is next most sensitive,
• LaModel-based LT (Gateroad 2) is the next most sensitive, and
• Bleeder loading in Gateroad 2 is the least sensitive.
Degree of sensitivity is still sensitive to loading condition, but is diluted by differences in gateroad
width.Standard value = 416 ft.
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Deep Case Study Results• LB in Gateroad 1 and LT in Gateroad 2 are most sensitive to changes in
β,
• LB in Gateroad 2 is the next most sensitive, and
• LH (Gateroad 1) is least sensitive.
Degree of sensitivity is still sensitive to loading condition, and panel criticality—more sensitive
in supercritical panels
Standard value = 21°
Supercritical vs. Subcritical threshold
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Deep Case Study Results• LB in Gateroad 1 and LT in Gateroad 2 are most sensitive to changes in β,
• LB in Gateroad 2 is the next most sensitive, and
• LH (Gateroad 1) is least sensitive.
Sensitivity increases by between 4%-7% below the supercritical threshold.
21°
Supercritical vs. Subcritical threshold
8°
Parameter LH LB LTAbutment angle β, centered on 21° (subcritical) M 7% M 10% M 9%
Abutment angle β, centered on 8° (supercritical), relative to 8° M 11% V 17% V 16%D, (subcritical) S <1% S <1% I 0%
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Conclusions
• Tailgate loading is affected by load transfer distance (D), as modeled using LaModel
• Overall, abutment angle (β) has more influence on pillar loading than load transfer distance (D)
• Changes in β have a greater effect in supercritcal panels than subcritical panels
• Relative degree of sensitivity to changes in β and D are dependent upon gateroad function
• More research is needed in western coalfields and deep mines
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Questions?
Presented by: Heather LawsonContact info: 509-354-8061, [email protected] Office of Mine Safety and Health Research is a division of the National Institute for Occupational Safety and Health (NIOSH) www.cdc.gov/niosh/mining
NIOSH is a division of the Centers for Disease Control and Prevention within the Department of Health and Human Services www.hhs.gov