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A New Method of Predicting the Height of the Fractured Water-Conducting Zone Due to High-Intensity Longwall Coal Mining in China

  • Wenbing Guo
  • Gaobo Zhao
  • Gaozhong Lou
  • Shuren Wang
Original Paper
  • 275 Downloads

Abstract

Violent movement of the roof rock and severe damage to the overlying strata occur in the large mined-out space left by rapidly advancing, high-intensity longwall coal mine extraction, as the goaf forms. Knowing the height of the fractured water-conducting zone (FWCZ) above the goaf is vital in the safety analysis of coal mining, particularly under a water body. The processes of overburden failure transfer (OFT) were analyzed for such high-intensity mining, divided into two stages: transmission development, and transmission termination. Rock failure criteria were used in theoretical calculations of the maximum lengths of ‘suspended’ (i.e., unsupported) rock strata, and of the maximum ‘overhang’ (i.e., cantilever) length of each stratum. Based on this, mechanical models of the unsupported strata and the overhanging strata were established. A new theoretical method of predicting the height of the FWCZ in this form of coal mining is put forward, based on OFT processes. A high-intensity mining panel (the 8100 longwall face at the Tongxin Coal Mine, Datong Coal Mining Group) was taken as an example. The proposed theoretical method, a numerical simulation method and an engineering analogy method were used to predict the height of the FWCZ. Comparison with in situ measurements at the Tongxin mine showed that the theoretical and numerical simulation results were in close agreement with measured data, verifying the rationality of the proposed approach.

Keywords

High-intensity mining Height of fractured water-conducting zone Overburden failure transfer Strata movement 

List of Symbols

FWCZ

Fractured water-conducting zone

OFT

Overburden failure transfer

Do max

Maximum overhang length

Ds max

Maximum unsupported (suspension) length

\(D_{{{\text{o}}i\;{\text{max}}}}^{\prime }\)

Maximum length of caving blocks

Fs, Fh

Shear force and horizontal force

\({G_i},\;G_{i}^{\prime }\)

Weight of stratum i unsupported part and overhang stability part

\({h_i},\;h\)

Thickness of stratum i, height of a stratum above coal seam roof

\({H_{\text{f}}},\;H\)

Heights of overburden failure and overlying strata

K, Kd, Ki

Bulking factor of overlying strata, immediate roof and stratum i, respectively

m

Mining thickness

M

Bending moment

Ps

Initial principal stress

\({q_i},\;q_{i}^{\prime },\;q_{i}^{\prime \prime }\)

Accumulated load on unsupported section of stratum i; accumulated load on stable overhanging section of stratum i; and accumulated load on adjacent blocks, respectively.

RT

Maximum tensile strength

\({\Delta _{n - 1,n}}\)

Separation distance between strata n − 1 and n

\(\gamma\)

Bulk density of rock

Notes

Acknowledgements

This work was supported by the National Natural Science Foundation of China (51774111) and the Henan Province Science and Technology Innovation Outstanding Talent Fund (184200510003). The authors wish to acknowledge these financial contributions and express their appreciation of those organizations for supporting this basic research.

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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2018

Authors and Affiliations

  1. 1.School of Energy Science and EngineeringHenan Polytechnic UniversityJiaozuoPeople’s Republic of China
  2. 2.Coal Production Safety Collaborative Innovation Center in Henan ProvinceHenan Polytechnic UniversityJiaozuoPeople’s Republic of China
  3. 3.International Joint Research Laboratory for Underground Space Development and Disaster Prevention of Henan ProvinceHenan Polytechnic UniversityJiaozuoPeople’s Republic of China

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