Advertisement

Effect of Premining on Hard Roof Distress Behavior: A Case Study

  • Weidong PanEmail author
  • Xiaodong Nie
  • Xinyuan Li
Original Paper
  • 73 Downloads

Abstract

Considering the complex geological conditions of mining in the fully mechanized 828 working face of the Qingdong Coal Mine, a mining plan was developed for premining the upper No. 7 coal seam to control the hard roof and gas of the No. 8 coal seam. Failure depth of the No. 7 coal seam floor and the caving interval of the hard roof were analyzed using a proposed model based on the Terzaghi’s principle and rock beam theory, respectively. The movement rules of the overlying strata under premining (No. 7 coal seam) and non-premining conditions were analyzed using physical material similarity simulations experiment. Furthermore, field monitoring was performed to determine the working resistance of the hydraulic supports. The estimated results from the proposed method showed that the failure depth of the floor of the 726 working face was 13.8 m, which is in agreement with that noted during the field observation. The caving interval of the hard roof decreased from 24.9 m to 10.6 m after premining the No. 7 coal seam. In the simulation, the caving interval of the hard roof of the No. 8 coal seam decreased from 20 m to 10 m after premining the No. 7 coal seam. The hydraulic supports were effective in the actual production process, and the initial and periodic weighting intervals were 20.4 m and 10.4 m, respectively. These findings demonstrate that after premining the No. 7 coal seam, the initial and periodic weighting intervals decreased, thereby reducing the pressure intensity of the roof. This method effectively weakens the hard roof of the No. 8 coal seam. The issues pertaining to the hard roof during the mining of the 828 working face could be overcome by premining a protective coal seam of the upper No. 7 coal seam.

Keywords

Hard roof Extremely thick coal seam Fully mechanized top-coal caving Physical material similarity simulation 

List of Symbols

H

Failure depth

r0

Waist length of the isosceles triangle

α

Angle between the waist line and the helical radius

φ

Inner-friction angle

L

Distance between the peak of abutment pressure and the working face

M1

Maximum positive bending moment

M2

Maximum negative bending moment

l

Distance between the center of the hanging main roof and the coal rib

X

Distance from the coal rib to the breaking position

RT

Uniaxial tensile strength

K

Stiffness of the elastic support

Y

Main roof deflection

αL

Geometrical similarity ratio

L1T

Weighting interval

αT

Motion similarity ratio

αγ

Density similarity ratio

I

Inertia moment

x2

Distance from the coal rib to the breaking position when the roof is broken deep in the coal rib

r

Distance between logarithmic spiral and original point

Notes

Acknowledgements

The authors gratefully acknowledge the financial support from the National Key Research and Development Plan (No. 2018YFC0604501) and the Yue Qi Distinguished Scholar Project, China University of Mining & Technology, Beijing (No. 800015Z1138).

References

  1. Alehossein H, Poulsen B (2010) Stress analysis of longwall top coal caving. Int J Rock Mech Min Sci 47:30–41CrossRefGoogle Scholar
  2. Bai Q, Tu S, Chen M, Zhang C (2016) Numerical modeling of coal wall spall in a longwall face. Int J Rock Mech Min Sci 88:242–253CrossRefGoogle Scholar
  3. Bai Q, Tu S, Wang F, Zhang C (2017) Field and numerical investigations of gateroad system failure induced by hard roofs in a longwall top coal caving face. Int J Coal Geol 173:176–199Google Scholar
  4. Chen H (2012) Stability analysis and control of the soft and broken surrounding rock in Qingdong mine. Thesis MS, AnHui University of Science and Technology, ChinaGoogle Scholar
  5. Cheng Y, Jiang F, Pang J (2012) Research on lateral strata pressure characteristic in goaf of top coal caving in extra thick coal seam and its application. J China Coal Soc 37(7):1088–1093. (in Chinese)Google Scholar
  6. Dou L (2006) Coal mining rockburst prevention and control. China University of Mining and Technology Press, Xuzhou. (in Chinese)Google Scholar
  7. Dou L, He X (2001) Theory and technology of rock bursts prevention. China University of Mining and Technology Press, Xuzhou. (in Chinese)Google Scholar
  8. Dou L, Lu C, Mu Z, Gao M (2009) Prevention and forecasting of rock burst hazards in coal mines. Min Sci Technol 19:585–591. (in Chinese)Google Scholar
  9. Du F, Bai H (2012) Mechanism research of overlying strata activity with fully mechanized caving in thin bedrock with thick alluvium. J China Coal Soc 37(7):1105–1110. [(in Chinese)Google Scholar
  10. Fan J, Dou L, He H, Du T, Zhang S, Gui B, Sun X (2012) Directional hydraulic fracturing to control hard-roof rockburst in coal mines. Int J Min Sci Technol 22:177–181CrossRefGoogle Scholar
  11. Han CL, Zhang N, Li BY, Si GY, Zheng XG (2015) Pressure relief and structure stability mechanism of hard roof for gob-side entry retaining. J Cent South Univ 22(11):4445–4455CrossRefGoogle Scholar
  12. He H, Dou L, Fan J, Du T, Sun X (2012) Deep-hole directional fracturing of thick hard roof for rockburst prevention. Tunn Undergr Space Technol 32:34–43CrossRefGoogle Scholar
  13. He MC, Chen SY, Guo ZB, Yang J, Gao YB (2017) Control of surrounding rock structure for gob-side entry retaining by cutting roof to release pressure and its engineering application. J China Univ Min Technol 46:959–969. (in Chinese)Google Scholar
  14. Hebblewhite B (2000) Review of Chinese thick seam underground coal mining practice. Aust Coal Rev 10:36–37Google Scholar
  15. Huang Q, Wu B, Cheng W, Lei B, Shi H, Chen L (2018) Investigation of permeability evolution in the lower slice during thick seam slicing mining and gas drainage: a case study from the Dahuangshan coalmine in China. J Nat Gas Sci Eng 52:141–154CrossRefGoogle Scholar
  16. Jiang JQ, Dai J, Zhang P, Zhang LP (2014) Overlying hard and thick strata breaking movement and broken-roof control. Rock Soil Mech 35:264–270. [in Chinese]Google Scholar
  17. Kang H (2013) Stress distribution characteristics and strata control technology for roadways in deep coal mines. Coal Sci Technol 41(9):12–17. [in Chinese]Google Scholar
  18. Kelly M, Balusu R, Hainsworth D (2001) Status of longwall research in CSIRO. In: Proceedings of the 20th International Conference on Ground Control in Mining, Morgantown. p: 16Google Scholar
  19. Li H, Jiang D, Li D (2014) Analysis of ground pressure and roof movement in fully-mechanized top coal caving with large mining height in ultra-thick seam. J China Coal Soc 39(10):1956–1960. [in Chinese]Google Scholar
  20. Li N, Wang EY, Ge MC, Liu J (2015) The fracture mechanism and acoustic emission analysis of hard roof and a physical modeling study. Arab J Geosci 8:1895–1902CrossRefGoogle Scholar
  21. Li L, Wu K, Hu ZQ, Xu YK, Zhou DW (2017a) Analysis of developmental features and causes of the ground cracks induced by oversized working face mining in an Aeolian sand area. Environ Earth Sci 76:135CrossRefGoogle Scholar
  22. Li XM, Wang ZH, Zhang JW (2017b) Stability of roof structure and its control in steeply inclined coal seams. Int J Min Sci Technol 27:359–364CrossRefGoogle Scholar
  23. Pan Y, Li Z, Zhang M (2003) Distribution, type, mechanism and prevention of rock burst in China. Chin J Rock Mech Eng 22:1844–1851. (in Chinese)Google Scholar
  24. Peng SS (2013) Coal mine ground control, 3 edn. China University of Mining and Technology Press, Xuzhou. [in Chinese]Google Scholar
  25. Ptacek J, Konicek P, Stas L, Waclawik P, Kukutsch R (2015) Rotation of principal axes and changes of stress due to mine-induced stresses. Can Geotech J 52:1440–1447CrossRefGoogle Scholar
  26. Prandtl L (1924) Spannungsverteilung in plastischen Körpern. In: Proceedings of the 1st International Congress on Applied Mechanics (pp. 43–54)Google Scholar
  27. Reuss VA (1930) Berücksichtigung der elastischen Formänderung in der Plastizitätstheorie. J Appl Math Mech/Zeitschrift für Angewandte Mathematik Mechanik 10(3):266–274Google Scholar
  28. Shimada H, Matsui K, Anwar H (1998) Control of hard-to-collapse massive roofs in longwall faces using a hydraulic fracturing technique. In: Proceedings of the 17th International Conference on Ground Control in Mining, West Virginia, MorgantownGoogle Scholar
  29. Simsir F, Ozfirat M (2008) Determination of the most effective longwall equipment combination in longwall top coal caving (LTCC) method by simulation modelling. Int J Rock Mech Min Sci 45.6:1015–1023CrossRefGoogle Scholar
  30. Singh T (1988) Soutirage—a dream mining method of thick coal seams. Trans Mining Geol Metal Inst India 85:88–110Google Scholar
  31. Singh GSP, Singh UK (2012) Influence of strata characteristics on face support requirement for roof control in longwall workings—a case study. Min Technol 121(1):11–19CrossRefGoogle Scholar
  32. Terzaghi K (1951) Theoretical soil mechanics. Chapman And Hall, Limited. LondonGoogle Scholar
  33. Tu S, Wang F, Dou F (2010) Fully mechanized top-coal caving: Underground stress at gateways under barrier pillars of an upper coal seam. J China Uni Min Technol 39(1):1–5. (in Chinese)Google Scholar
  34. Vakili A, Hebblewhite BK (2010) A new cavability assessment criterion for Longwall Top Coal Caving. Int J Rock Mech Min Sci 47(8):1317–1329CrossRefGoogle Scholar
  35. Wang J (2009) Theory and Technology of Thick Coal Seam Mining. Metallurgical Industry Press, Beijing, p 9. (in Chinese)Google Scholar
  36. Wang J (2011) The technical progress and problems to be solved of thick coal-seam mining in China. In: Proceedings of the 30th International Conference on Ground Control in Mining, Morgantown; 29–31 July 2011Google Scholar
  37. Wang J, Wang Z (2015) Stability of main roof structure during the first weighting in shallow high-intensity mining face with thin bedrock. J Min Saf Eng 32(2):175–181Google Scholar
  38. Wang J, Yang S, Li Y, Wei L, Liu H (2014) Caving mechanisms of loose top-coal in longwall top-coal caving mining method. Int J Rock Mech Min Sci 71:160–170CrossRefGoogle Scholar
  39. Wang J, Zhang J, Gao X (2015a) Fracture mode and evolution of main roof stratum above longwall fully mechanized top coal caving in steeply inclined thick coal seam (I)—Initial fracture. J China Coal Soc 40(6):1353–1360. [in Chinese]Google Scholar
  40. Wang J, Zhang J, Gao X (2015b) Fracture mode and evolution of main roof stratum above longwall fully mechanized top coal caving in steeply inclined thick coal seam (II)—Periodic fracture. J China Coal Soc 40(8):1737–1745. [in Chinese]Google Scholar
  41. Wang J, Zhang J, Li Y (2015c) Ground control in China’s coal mine: progress and prospects. In: Proceedings of 48th US Rock Mechanics/ Geomechanics Symposium. San Francisco, California, U.S., 28 June-1 July 2015. American Rock Mechanics Association, Virginia 1830–1835Google Scholar
  42. Wang J, Zhang J, Song Z, Li Z (2015d) Three-dimensional experimental study of loose top coal drawing law for longwall top coal caving mining technology. J Rock Mech Geotech Eng 7(3):318–326.  https://doi.org/10.1016/j.jrmge.2015.03.010 CrossRefGoogle Scholar
  43. Wang J, Zhang J, Li Z (2016) A new research system for caving mechanism analysis and its application to sublevel top-coal caving mining. Int J Rock Mech Min Sci 88:273–285CrossRefGoogle Scholar
  44. Wang H, Wu Y, Xie P, Cao P, Guo F (2017) Research on strata movement and support stability of fully mechanized sublevel caving workface with variable angle in steeply dipping seam. J China Uni Min Technol 46(3):507–513. (in Chinese)CrossRefGoogle Scholar
  45. Xia Z (1991) Plastic mechanics. TongJI Uni. Press, Shanghai. (in Chinese)Google Scholar
  46. Xu Y, Dai H (2017) Subsidence control and special mining. China Uni. of Min. and Tech. Press, Xuzhou. [in Chinese]Google Scholar
  47. Yang S, Zhang P, Li F (2010) Load determination of powered supports for fully mechanized top coal caving mining face in horizontal slice of steep inclined thick seam. Coal Sci Technol 38(11):37–40. [in Chinese]Google Scholar
  48. Yu B (2016) Behaviors of overlying strata in extra-thick coal seams using top-coal caving method. J Rock Mech Geotech Eng 8:238–247CrossRefGoogle Scholar
  49. Yuan Y, Tu S, Ma X, Sun L, Bai Q (2012) Coal wall stability of fully mechanized working face with great mining height in “three soft” coal seam and its control technology. J Min Saf Eng 29(1):21–25. [in Chinese]Google Scholar
  50. Zhang C, Tu S, Bai Q, Yuan G, Zhang L (2015) Evaluating pressure-relief mining performances based on surface gas venthole extraction data in longwall coal mines. J Nat Gas Sci Eng 24:431–440CrossRefGoogle Scholar
  51. Zhang J, Wang J, Wei W, Chen Y, Song Z (2018) Experimental and numerical investigation on coal drawing from thick steep seam with longwall top coal caving mining. Arab J Geosci 11.5:96CrossRefGoogle Scholar
  52. Zhao H (2011) Numerical simulation on pressure behavior of mining field under the conditions of hard roof. Disaster Adv 4(1):15–20Google Scholar
  53. Zhao T, Liu C, Yetilmezsoy K, Zhang B, Zhang S (2017) Fractural structure of thick hard roof stratum using long beam theory and numerical modeling. Environ Earth Sci 76:751CrossRefGoogle Scholar
  54. Zhou H, Yang Q, Cheng Y, Ge C (2014) Methane drainage and utilization in coal mines with strong coal and gas outburst dangers: a case study in Luling mine, China. J Nat Gas Sci Eng 20:357–365CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2019

Authors and Affiliations

  1. 1.State Key Laboratory of Coal Resources and Safe MiningChina University of Mining and TechnologyBeijingChina
  2. 2.Key Laboratory for Precise Mining of Intergrown Energy and ResourcesUniversity of Mining and TechnologyBeijingChina
  3. 3.Coal Industry Engineering Research Center of Top-coal Caving MiningBeijingChina

Personalised recommendations