![Page 1: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/1.jpg)
Analysis of Potential Implications of Observed Load Transfer Distance and Abutment Angle on Longwall Pillar Loading
Heather E. LawsonJeffrey K. WhyattMark K. Larson
![Page 2: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/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: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/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
![Page 4: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/4.jpg)
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
![Page 5: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/5.jpg)
Supplemental StudyLaModel Analysis• Re-examines role of
LTD in TG loading• Indicates that LTD
influences TG loading• Suggests a modified
FT
![Page 6: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/6.jpg)
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
![Page 7: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/7.jpg)
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 DDegree of sensitivity is dependent on loading condition
Standard value = 208 ft.
![Page 8: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/8.jpg)
Shallow Case Study Results• Changes in D have little effect on smaller scale• Loading is moderately to very sensitive to small changes in βLoading 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%
![Page 9: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/9.jpg)
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.
![Page 10: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/10.jpg)
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
![Page 11: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/11.jpg)
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%
![Page 12: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/12.jpg)
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
![Page 13: Heather E. Lawson Jeffrey K. Whyatt Mark K. Larson](https://reader036.vdocuments.pub/reader036/viewer/2022062323/568166d8550346895ddaf447/html5/thumbnails/13.jpg)
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