Logical designing of yield pillar base on coal pillars yielding process

The longwall mining method is one of the best methods for exploitation of undergroundhorizontal to near horizontal coal layers. The high production and safety are the typicaladvantages. Entries of both sides longwall panel having important role in product andsafety. With increasing depth of mine, difficulty of supporting condition of entries increases.One of the basic solutions for such entries stability, particularly at deep mines, is to use yield chain pillars. Since, the behavior of coal pillar at post-peak regime is not known, so th logical designing of these yield chain pillars are not well established.In this paper, two strain-softening models with numerical and analytical fundamentals areanalyzed. These models are studied for a row of yield chain pillar at longwall mining systemat 700 m dept of surface ground. In this study, only development phase of longwall mining system is contemplated while the deformation, yielding and failure possibility are considered before longwall operation runs. Results show in deep longwall mine yield chain pillar can be used. In addition, both analyzed strain-softening models, having required potential for rather optimum understanding of pillar yielding behavior. Therefore, could be a base for yield pillar logical design. Study development shows this approached yield pillar design is sensitive to pillar behavior after coal peak strength. In addition, due to two-dimensional modeling, front abutment load influence could not be evaluated.