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Influence of the Elastic Dilatation of Mining-Induced Unloading Rock Mass on the Development of Bed Separation

1
Key Laboratory of Deep Coal Resource Mining, Ministry of Education of China; School of Mines, China University of Mining and Technology, Xuzhou 221116, China
2
State Key Laboratory of Coal Resource and Safe Mining, China University of Mining and Technology, Xuzhou 221116, China
3
Department of Civil Engineering, Faculty of Engineering, University of Nottingham, University Park, NG7 2RD Nottingham, UK
*
Author to whom correspondence should be addressed.
Energies 2018, 11(4), 785; https://doi.org/10.3390/en11040785
Received: 6 January 2018 / Revised: 19 February 2018 / Accepted: 27 March 2018 / Published: 29 March 2018
(This article belongs to the Section Energy Sources)
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Abstract

Understanding how mining-induced strata movement, fractures, bed separation, and ground subsidence evolve is an area of great importance for the underground coal mining industry, particularly for disaster control and sustainable mining. Based on the rules of mining-induced strata movement and stress evolution, accumulative dilatation of mining-induced unloading rock mass is first proposed in this paper. Triaxial unloading tests and theoretical calculation were used to investigate the influence of elastic dilatation of mining-induced unloading rock mass on the development of bed separation in the context of district No. 102 where a layer of super-thick igneous sill exists in the Haizi colliery. It is shown that the elastic dilatation coefficient of mining-induced unloading hard rocks and coal were 0.9~1.0‰ and 2.63‰ respectively under the axial load of 16 MPa, which increased to 1.30~1.59‰ and 4.88‰ when the axial load was 32 MPa. After successively excavating working faces No. 1022 and No. 1024, the elastic dilatation of unloading rock mass was 157.9 mm, which represented approximately 6.3% of the mining height, indicating the elastic dilatation of mining-induced unloading rock mass has a moderate influence on the development of bed separation. Drill hole detection results after grouting, showed that only 0.33 m of the total grouting filling thickness (1.67 m) was located in the fracture zone and bending zone, which verified the result from previous drill hole detection that only small bed separation developed beneath the igneous sill. Therefore, it was concluded that the influences of elastic dilatation of mining-induced unloading rock mass and bulking of caved rock mass jointly contributed to the small bed separation space beneath the igneous sill. Since the accurate calculation of the unloading dilatation of rock mass is the fundamental basis for quantitative calculation of bed separation and surface subsidence, this paper is expected to be a meaningful beginning point and could provide a useful reference for future, related research. View Full-Text
Keywords: unloading dilatation; key stratum; bed separation; super-thick igneous rock; mining-induced rock mass unloading dilatation; key stratum; bed separation; super-thick igneous rock; mining-induced rock mass
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Zhu, W.; Yu, S.; Xu, J. Influence of the Elastic Dilatation of Mining-Induced Unloading Rock Mass on the Development of Bed Separation. Energies 2018, 11, 785.

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