4 - Rock failure above and below chain pillars: Implications for strength and fluid flow between goafs

Abstract

The aim of this paper is to discuss the rock mechanics issues that can influence the strength of pillars in coal mines. The paper utilizes stress change monitoring results, microseismic monitoring results, and computer modeling to assess the stress history about a chain pillar. The implications and fracture modes developed are discussed, with the outcome being that chain pillar strength can be significantly reduced by the stress path and changes in boundary conditions to the pillar when longwall extraction occurs. It is envisaged that this effect is contained in measured and empirical data bases. However, it is important to recognize the stress path process when applying results to various site conditions and mine layouts. The implications for strength and fluid flow is discussed.