Stability of parting rock between level contiguous coal pillar workings

Abstract

The factors affecting stress distribution in thin parting between contiguous pillar working have been identified as depth of cover, parting thickness, lateral shift between pillars, percentage extraction and modulus ratio. A large number of two-dimensional finite element models covering these variables ultimately give an expression for the maximum tensile stress. Barton's rock classification [1] is next modified considering this stress and three-dimensional finite element analysis of four failed cases. In all, six collapsed cases and four stable cases have been used to estimate the safe roadway junction spans as against the existing spans, using the modified classification equation. Safety factors of parting rock in all case studies have also been calculated using a recently developed failure criterion for jointed rock masses [2] as well as the Hoek and Brown criterion [3], comparing their performance. Design guidelines are presented for contiguous pillar workings.