Deformation characteristics and mechanism of deep subsize coal pillar of the tilted stratum

Based on the analysis of the monitoring data of surface displacement and internal multipoint displacement of coal pillars near three inclined strata roadways, which have similar burial depth and different surrounding rock conditions in a coal mine in the east China, the coal pillars' stress change was combined with discontinuous numerical simulation software to simulate the deformation process of one of the roadways. Field monitoring data and numerical simulation results show that when this working face roadway is dug, the coal pillar enters plastic state after being affected by multiple mining influence, but it can still maintain the basic stability of the roadway and control coal pillar deformation under the current widely used supporting method. With the shortening of the distance between the monitoring area and the working face, the vertical and horizontal stress in the coal pillar increase gradually, but the maximum value of the vertical stress decreases by 1.4 MPa, and deformation amount and velocity of the coal pillar show the characteristics of nonlinear rapid increase. The shape of the vertical stress core area in the coal pillar changed from oval to rectangle, and the width of the core area increased, and it moved 1 m to the goaf side. In the process of coal pillar deformation, there is no zero displacement surface within the monitoring range of 6 m.