Numerical simulation research and application on protected layer pressure relief affection under different coal pillar width

In order to research protected layer pressure relief effect under influence of different width of coal pillar, this paper carried on FLAC3D numerical simulation of vertical stress field and deformation field under different coal pillar width. The protected layer evolutional characteristics of vertical stress, vertical displacement and pressure relief affection which coal pillar affected were analyzed. The results show that: (1) Coal pillar affected zone is high stress concentrated zone. Because of coal pillar width influence, trended vertical stress distribution is from v shape to partial saddle shape; tendency vertical stress distribution is flat disc shape. Vertical stress is non-linear with coal pillar width, vertical stress is most concentrated when coal seam reserved 20m coal pillar, vertical stress distribution is from single peak shape to double peak shape. (2) Coal pillar affected zone is low strain region. Coal pillar decreases protected layer overall deformation, not just reduce deformation of coal pillar affected zone. Vertical deformation is negative correlation with coal pillar width. Trended vertical displacement distribution is similar to shape; tendency vertical displacement distribution is flat disc shape. (3) Unprotected range increases with the increase of coal pillar width, pressure relief angle is 49 degrees-60 degrees, pressure relief angle of both sides is negative correlation with mined out areas. (4) Engineering measurement shows: simulative results and experimental results are consistent. Research results have theoretical reference and practical significance on unprotected layer effect measurement and outburst elimination. (c) 2014 The Authors. Published by Elsevier Ltd.