Estimation of Tunnel Stability and Optimization of Support Parameters for Tunnel below Gob Pillar in Closely-Spaced Coal Seams

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Authors

  • M. L. Zhang
     School of Mines, Key Laboratory of Deep Coal Resource Mining, Ministry of Education of China; China University of Mining & Technology ,CN
  • Y. D. Zhang
     Mines; China University of Mining & Technology ,CN
  • M. Ji
     School of Mines, Key Laboratory of Deep Coal Resource Mining, Ministry of Education of China; China University of Mining & Technology ,CN
  • H. J. Guo
     School of Mines, Key Laboratory of Deep Coal Resource Mining, Ministry of Education of China; China University of Mining & Technology ,CN

Keywords:

Gob pillar; CRBBS; tunnel instability coefficient; optimization of support parameters; tunnel position

Abstract

After the upper coal seam mining, stress concentrations under the residual pillar generate an inhomogeneous stress field and the stress on the tunnel increases. This can lead to tunnel destruction if the external forces exceed the strength of the composite rock–bolt bearing structure (CRBBS). The Weibull distribution function was introduced to modify the calculation formula of the CRBBS strength and stress distribution of the CRBBS. The radial stress within the CRBBS under the inhomogeneous stress field was calculated. The tunnel instability coefficient () was derived to quantitatively describe the relationship among the tunnel position, tunnel parameters, support parameters, and rock mechanical properties. The coefficient is the ratio of the maximum radial stress within CRBBS to the CRBBS strength; the CRBBS is stable only when <1. The instability coefficient of the 21178 return tunnel Huopu colliery was calculated to obtain the optimised support parameters.The bolt strength was adjusted from 335MPa to 500MPa and the bolt length was changed from 2.2m to 2.5m; thus, the large deformation of the 21178 return tunnel was controlled. The optimum distance between the 21178 return tunnel and the pillar edge was at least 12.4m. The proposed method was validated by comparison with results by the tunnel stability index method (>20m), abutment pressure influence edge method (14.6m), and rateo fstress change method (>16.2m). Since the resistance of the bolt support is quantified, the tunnel position evaluated by the tunnel instability coefficient is more practical.

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Published

2022-10-20

How to Cite

Zhang, M. L., Zhang, Y. D., Ji, M., & Guo, H. J. (2022). Estimation of Tunnel Stability and Optimization of Support Parameters for Tunnel below Gob Pillar in Closely-Spaced Coal Seams. Journal of Mines, Metals and Fuels, 67(2), 59–68. Retrieved from http://informaticsjournals.com/index.php/jmmf/article/view/31469

Issue

Volume 67, Issue 2, February 2019

Section

Articles

License

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

 

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