Abstract
The Longwall Top Coal Caving (LTCC) method has greatly improved the production of ultra-thick underground coal resources. However, face fall and support closure have been becoming highly frequent accidents at the working face, and seriously threaten the safety of miners. The key to avoiding these problems is to reveal the structural evolution of the roof strata and then choose a reasonable working resistance for the hydraulic supports. According to physical modeling, theoretical analysis and field observation of the LTCC panel, four kinds of structural models can be found and defined, in consideration of the coincident movement of key strata (KS) and the mining activities of upper face in overburden strata. The KS are performed as cantilever structures, hinged structures and voussoir beam structures at three different positions in roof strata. The structural characteristics of the KS and its movement laws are shown in the four structural modes. The loads acting on the support in the four typical structural models are also analyzed. The structural instability of the broken roof strata on the upper caving panel caused by the lower ultra-thick coal seam mining is considered to be the main reason for its face’s falls and support failures. Consequently, a method is proposed for calculating the working resistance of the support in the LTCC face, which is verified by the mining pressure monitoring in practice.
Highlights
Chinese coal production fell by 7.9%, and energy consumption in China grew by just 1.3% in 2016.Despite this, China remained the world’s largest growth market for energy for the 16th consecutive year
In order to describe the behaviors of the roof strata more visually, we have summarized four typical structural models of the Longwall Top Coal Caving (LTCC) panel in Tashan Coal Mine
Three key strata (KS) control control the movement of the overburden strata and determine the mining pressure in the LTCC
Summary
China remained the world’s largest growth market for energy for the 16th consecutive year. The measures for reducing the capacity of the smallest, least productive mines and encouraging greater consolidation have improved the productivity and profitability of the remaining mines; at the same time, China is resuming its position as the world’s largest importer of coal [1]. More efficient mining methods are encouraged in China. Longwall Top Coal Caving (LTCC) is an economical underground mining method that has been introduced and practiced in underground coal mines in. In China, the LTCC technology has been successfully applied to extracting ultra-thick coal seams [5–8] in which the caving height is more than 10.0 m and might even reach 20.0 m in certain coal mines [9]. The stability of the surrounding rocks [10–12] and the cavability of Energies 2018, 11, 1041; doi:10.3390/en11051041 www.mdpi.com/journal/energies
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