As the maximum space is required for underground facilities such as crushing room, it is necessary to leave minimum size and number of pillar. On the other hand, stability should be secured for constant cavern management. In this study, authors conducted series of analysis on pillar stability and roof displacement for the cavern with different pillar shape about the same size; a single square column pillar, a single cylindrical pillar, and twin cylindrical pillars. Principal stress reduced in cavern was the same in both a square pillar and a single cylindrical pillar. In case of displacement, displacement in a square column pillar was slightly larger than others. When the cavern becomes bigger, construction of multiple pillars becomes more profitable.

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