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Underground soft rock mining
Published in A.J.S. (Sam) Spearing, Liqiang Ma, Cong-An Ma, Mine Design, Planning and Sustainable Exploitation in the Digital Age, 2023
A.J.S. (Sam) Spearing, Liqiang Ma, Cong-An Ma
Two parallel sets of tunnels/gates (development panels) are cut into a seam with continuous mining machines, then connected with a set of crosscuts (especially for ventilation) at the far end. Mining then proceeds back toward the entrance (in retreat). Longwall mining employs some very productive machines. Large drum shearers, for example, run on a track (part of the AFC structure) along the length of the coal face for typically some 180–300m. The shearers cut the coal, which falls onto an AFC (conveyor system or pan) that also runs the entire length of the face. The longwall crew works under a roof of heavy steel supports called shields. As the coal is removed, shearers, pans and shields are moved forward systematically and automatically by hydraulic rams. The roof is allowed to collapse behind the shields. In addition to increasing production, longwall mining is considered to be safer because the miners work under strong steel shields.
Pillar design issues in coal mines
Published in Xia-Ting Feng, Rock Mechanics and Engineering, 2017
Longwall mining is a highly mechanized production technique that was developed in Europe in the early twentieth century and gained popularity very fast in all coal producing countries (Bise, 2013). This mining method similar to room and pillar mining is applied for extracting flat and nearly flat seams. Figure 4 shows a typical layout of a longwall mine. As can be seen, each panel is surrounded by three entries, namely headgate, tailgate and bleeder entries, which are also called panel entries. Panel entries affect the safety and productivity of longwall mining remarkably. Thus, in order to increase the safety, the panel entries are made as multi-entries. The panel entries consist of two, three, four, or sometimes five entries. The most common is the three-entry system. By law, this is the minimum number of entries required for developing the panel entries, because any entry development requires at least one separate entry for intake and return air escapeway, and a separate belt entry in neutral air (Peng, 2006).
How Coal is Mined
Published in H. Townshend-Rose, The British Coal Industry, 2017
Advantages of longwall mining are the high percentage of coal extraction which it makes possible, the small amount of development work necessary prior to productive operations, and the control of subsidence which is possible. Disadvantages are the amount of labour and material required for support of roadways and at the working face, and the fact that, because factory methods of supervision cannot be applied to mining, lower standards of work and discipline are sometimes associated with the larger concentrations of men that the system requires. The rigid cycle of operations necessary for longwall working is easily disorganized by absenteeism and slow working.
Research on the Control Process of Mining and Combustion Disturbance Zone Based on the Three-Dimensional Dynamic Distribution Model of Void Fraction
Published in Combustion Science and Technology, 2022
Longwall mining is a widely used method for mechanized and large-scale mining of underground seams. As the long coal seam is mined piece by piece, a rectangular mining area is formed, and the length of the goaf gradually increases with the advancement of the longwall mining face. As mining progresses, the overlying strata destabilize and sink, and move toward the gob. Discontinuous subsidence of the overburden creates voids. For the horizontal rectangular goaf formed by longwall mining, according to the key layer theory, the settlement of the i-th key layer can be expressed as (Li, Qian, and Shi 2000):
Development of predictive methods for strain at the surface due to longwall coal mining
Published in Mining Technology, 2018
James Barbato, Bruce Hebblewhite, Rudrajit Mitra, Ken Mills, Arthur Waddington
Longwall mining is a widely used method for the underground extraction of coal. This mining method results in subsidence at the surface that comprises both vertical and horizontal components. Mine subsidence can result in impacts on natural and built features that are located directly above the longwalls. These impacts generally result from the relative (i.e. differential) horizontal movements, rather than from the absolute horizontal movements or the vertical component (Peng 1986; Bai et al. 1989; Tandanand and Powell 1991; Li et al. 2011).