Study on Safe Mining of Working Face Under the Influence of Upper Stratified Coal Pillar

In order to study the influence of the upper stratified residual coal pillars on the mining of the lower stratified working face, the 1304 working face of Shandong Jinqiao Coal Mine was taken as the engineering background. FLAC^3D simulation software was used to study the plastic zone and bearing pressure distribution of coal pillars and the evolution of bearing pressure during the step-by-step mining of the lower layer working face. The research shows that when the stratified working face is not mined, the lateral bearing pressures of the two goafs are superimposed, and two stress concentration zones are formed at the edge of the coal pillar, and the stress concentration factors are 2.2 and 2.8 respectively. The coal column undergoes all plastic failure to form a yielding coal pillar, which can support the load applied by the overburden and is not easy to induce a destabilizing dynamic disaster. When the lower stratified working face is mined, the coal pillars are changed from two-sided mining to three-sided emptying. The stress concentration factor is increased from 3.8 to 4.5, which may induce the “creep-mutation” instability type rock burst of coal pillar under the action of strong supporting pressure. Therefore, during the mining period, the coal pillar impact hazard monitoring should be strengthened, and the large-diameter borehole pre-relieving pressure measures should be taken.