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Journal of the Southern African Institute of Mining and Metallurgy

On-line version ISSN 2411-9717
Print version ISSN 2225-6253


XIE, S.R. et al. Distinguishing and controlling the key block structure of close-spaced coal seams in China. J. S. Afr. Inst. Min. Metall. [online]. 2016, vol.116, n.12, pp.1119-1126. ISSN 2411-9717.

Based on the complicated geological production conditions and abnormal strata behavior of the fully mechanized caving face No. 102 in the Xinyang Coal Mine, we analyze the breaking and forming process of distinguishing key block structures in close spaced coal seams. This analysis establishes an integrated mechanical model of these distinguishing structures. Furthermore, the horizontal force TABgenerated by downward key blocks A and B is quantified, as is the Pressure PGexerted by key block B on caved gangue. Finally, the interaction mechanism is revealed. Analysis of the results using Mathematica reveal the following: 1. Both TABand PG exhibit approximately inverse relationships to coal pillar width b; 2. TAB exhibits an approximately exponential relationship with mining height M of which the base is greater than 1; 3. PG exhibits an approximately arctangent relationship with mining height M. Combining these results with field observations, we conclude that the area in the vicinity of supports 100#-120# in the upper area of working face No. 102 is the likely zone of abnormal strata behavior. Thus, this area was classified as a key control area. Based on these results, the graded support control technique is proposed. Application of this technique in the field resulted in a reduction in the rate of hydraulic support system malfunction from 47% to 7% in the key control area. In addition, during times of periodic mining pressure, the roof caving height value never exceeded 0.3 m and the maximum spalling depth never exceeded 0.2 m. Overall, the results indicate that this new technique has markedly increased the stability of surrounding support rock material.

Keywords : close-spaced coal seams; distinguishing key block structure; graded supporting control; malfunction detection.

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