Research on unsymmetrical loading effect induced by the secondary mining in the coal pillar

The coal pillar is usually subject to mining influence on both sides.The loading distribution on coal pillar is unsymmetrical under the unilateral influence.Its own bearing characteristic is closely related to the surrounding rock structure.To determine the width of the pillar in coal mine, the dynamic stability of the pillar should be taken into account besides the consideration of the maximum static loading capacity. Theoretical calculating formula of the plastic zone of the coal pillar induced by one-sided mining is presented according to the limiting equilibrium theory in this paper. The unsymmetrical loading effect during the advancing process of the mining is analyzed through the field monitoring by the deployment of the stress sensors in the pillar along the longitudinal direction. The method to determine the proper width of the coal pillar is presented at last.