Study on influence of close collapse pillar on advancement of working face

In view of the phenomenon that the working face passes through the close collapse pillar, the pressure changes frequently, the paper employed the No.635 and No.637 collapse pillars in the No.63310 working face of a mine as the engineering background, using a combination of theoretical analysis, numerical simulation and on-site monitoring ,the stress distribution characteristics around the single collapse pillar, the plastic extension area around the collapse pillar and the stress distribution state between the collapse pillars were studied. The influence law of the close collapse pillar on the advancement of the working face was analyzed. The surrounding rock mechanics model of the circular collapse pillar was established, and the radius of the plastic expansion zone of the surrounding rock around the single collapse pillar was determined. Combining the positional relationship between the close collapse pillars and the plastic expansion area of the single collapse pillar, the method ΔL for judging the stress state between the collapse pillars was proposed. It is determined that when ΔL0, the collapsed pillar is in an elastic stress state or an original rock stress state; according to the specific geological conditions of the two collapse pillars of the 63310 working face, the ΔL size between the collapse pillars is quantified, and the stress rise between the collapse pillars is determined. The numerical simulation shows the size of the plastic expansion zone around the collapse pillar and the stress distribution state between the cylinders. The safety distances of the working face distances No.637 and No.635 were determined to be 30 m and 50 m, respectively. The judgment method ΔL proposed by the theoretical analysis mutually authenticated. The research results can provide reference for the working face over the collapse pillars under similar conditions.