Abstract
When designing the mining of an ultrathick coal seam, the laws governing movement in the overlying strata during mining are a fundamental issue based on which several problems are addressed, including determining the mining method and the roadway arrangement, controlling the surrounding strata, and selecting the devices. The present paper considers possible problems related to strata overlying a large mining space subjected to repeated disturbances during the mining of an ultrathick coal seam, including repeatedly broken strata and the existence or inexistence of the structure. The BM coal seam in the No. 2 coal mine of the Dajing mining area in the East Junggar coalfield is studied. Physical simulations are performed on the movements of the overlying strata during slicing mining of the ultrathick coal seam, revealing the new feature of “break-joint stability-instability-secondary breakage” in the overlying strata. Mechanical models are constructed of the secondary breakage of the overlying strata blocks under both static and impact loading, and mechanical criteria are proposed for such breakage. Based on the research findings, methods for controlling the surrounding strata during slicing mining of an ultrathick coal seam are proposed, including increasing the mining rate and designing reasonable heights for the slicing mining.
Highlights
Introduction e mining areas of WesternChina have abundant coal resources
If the failed rock mass below the key #11 fine sandstone could support the latter effectively, the key stratum remained structurally stable during the periodic slicing mining (SM)
Two fractures formed in the overlying strata (OS), reaching the ground surface along the direction of the caving angle of the strata on the two sides of the working face
Summary
Received 20 September 2018; Revised 12 December 2018; Accepted 6 January 2019; Published 3 February 2019. UTCSs with a thickness of 40 m inevitably require the use of slicing mining (SM), thereby presenting the problem of how to control the stability of the overlying strata (OS) when mining a UTCS with a large mining space and repeated mining disturbances [4, 5] Both in China and internationally, there has been much theoretical and practical research regarding the laws governing the movement of OS in mining [6,7,8]. To achieve scientific mining of the BM coal seam (40 m thick), key issues such as SM scheme, roadway arrangement, surrounding rock control, and equipment selection must be solved To attain these goals, it is necessary to understand overlying strata movement and the underlying mechanism in the mining process of UTCS through basic tests. Several physical simulation experiments were carried out in this study, and the purpose of which was
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