Stability analysis of shaft pillars using three dimensional finite element modeling: a case study

A return air-shaft of 6 in diameter has been constructed in GDK-11A bord and pillar mine operated by Singareni Collieries Company Limited (SCCL), India. This shaft has passed through a corner of a coal pillar already existing at 190 in depth of working. In order to stabilize the pillar area near the shaft opening, it was proposed that I in thick concrete walls had to be built around the pillar corners. This study focused on analyzing the stability of shaft pillars in terms of stress concentration factors, yield zones and deformation characteristics in the pillars and as well as in the roof along the galleries. For this purpose three dimensional finite element models were developed to simulate two different conditions viz. the concrete walls are in full contact and not in contact with the roof The study was further elaborated for the non-linear analysis using the Drucker-Prager failure criterion to evaluate the yield zones around pillars and shaft opening area. A comparison between linear and nonlinear analysis results will also be discussed in this paper to illustrate the effects yield and stress concentration zones depending on different material properties of concrete wall.