Study of roof stability of the end of working face in upward longwall top coal
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ORIGINAL PAPER
Study of roof stability of the end of working face in upward longwall top coal De-zhong Kong 1 & Wei Jiang 2 & Yi Chen 2 & Zheng-yang Song 2 & Zhenqian Ma 1
Received: 6 December 2016 / Accepted: 30 March 2017 # Saudi Society for Geosciences 2017
Abstract Low recovery of longwall top coal caving (LTCC) remains one of the most difficult engineering problems in this mining method and impedes its application. The top coal left in the gob at face end accounts for a large portion of the total coal loss, and the instability of the leftover triangle coal at face end has long been a threat to the safety of miners and the mining equipment. In this paper, based on the engineering background of Ruilong mine, we explore the stability of the roof at the end of the face by using theoretical analysis, numerical simulation, and field measurement. Results reveal that in the inclined longwall top coal caving face, the immediate roof forms an Barch^ structure, and the basic roof forms a Bmasonry beam^ structure after the roof collapses; working resistance of the support calculated by the method of ultimate bearing capacity was adequate to meet the requirement of roof load; roof load of coal pillar was related to the length of key block and fracture position; and increasing the size of coal pillar could ensure the stability of both coal pillar and roof. Keywords LTCC, ULTCC . Top coal caving at face end . Roof stability
Introduction The improvement of mining equipment in recent years has greatly increased the application of longwall top coal caving * De-zhong Kong [email protected]
1
Mining College, Guizhou University, Guiyang, Guizhou, China
2
School of Resource and Safety Engineering, China University of Mining and Technology, Beijing, China
technology [Wang JC et al. 2004; 2014]. This mining method not only improves the production and efficiency but also reduces the spontaneous combustion disaster in longwall operations [Unver and Yasitli (2006); Khanal et al. 2014]. In western part of Turkey, Hakan Basarir et al. analyzed the stresses around main and tail gates during top coal caving by 3D numerical analysis [Basarir et al. 2015]. In Slovenia, a lensshaped coal deposit with a thickness of more than 160 m at the center and pinches out towards the margins is extracted by multi-level longwall top coal caving [Likar et al. 2012; Si and Jamnikar 2015; Gregor jeromel et al. studied the multi-level longwall top coal caving process by numerical simulations and in situ measurements during coal excavation at different locations in the Velenje Coal Mine [Jeromel et al. 2010]. However, the main constraint of the security, efficiency, and caving speed of LTCC is the poor stability of top coal and roof at the end of working face [Wang JC. 2009; 2010; 2013]. At the junction of the face and entry, the area of face end has complicated spatial relations of equipments and timeconsuming production procedures. Traditional face end of LTCC reserves its top coal at the end of working face and uses single prop with articulated beam
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