Abstract

ZHANG, D.  and  SUI, W.. Orthogonal array analysis of overburden failure due to mining of multiple coal seams. J. S. Afr. Inst. Min. Metall. [online]. 2019, vol.119, n.10, pp.801-810. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/17/036/2019.

This paper presents a numerical analysis that uses an orthogonal array to investigate overburden failure caused by longwall mining of multiple coal seams. An LN(s^k) array is said to be an orthogonal array with s levels, N rows, and k columns. This analysis identifies the contrasting factors that influence the height of the caving and water-conducting fractured zones. The factors include the mechanical properties of the interburden layers (factor A), thickness of the interburden layers (factor B), and mining height of the lower seam (factor C). The mechanical properties of the overburden failure are quantitatively investigated and the correlations among the factors are evaluated. The results show that factors A, B, and C all have a significant influence on the interactions during mining of multiple seams. This means that mining of the lower seam significantly changes the height of the caving zone of the entire system, with factors B and C having the most influence. Factor B has a more obvious effect on the water-conducting fractured zone than factor A, but factor C has the greatest effect among the factors. An equation to describe a dividing line, which is set to denote the relationship between the non-interaction ratio (K) and the cutting height of the lower seam (M) is proposed. This modified dividing line can be used to determine whether interactions exist among the overburden failure zones.

Keywords : numerical simulation; orthogonal array; multiple coal seams; water-conducting fractured zone; caving zone.

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