Coupling control of pillar stress and surface cracks in shallow coal seam group mining

In order to investigate the coupling control of reducing coal pillar pressure concentration and realizing uni- form surface subsidence to reduce surface cracks in shallow buried coal seams mining,the physical simulation and nu- merical calculation are employed. The interval strata breaking form,the concentrated stress distribution of coal pillars, the overburden and surface cracks and the ground surface subsidence in different coal pillar stagger distances are ob- tained. The relationship of the coal pillar stagger with the evolution of coal pillar stress concentration and of overburden fracture is discovered. According to the study,the determination of the reasonable upper and lower coal pillars stagger by interval layer breaking form can avoid the section coal pillar concentrated stress superposition and non-uniform stra- ta subsidence in coal pillar supporting influence area,and realize the coupling control of stress and cracks in shallow coal seam group mining. In this paper,the control model of concentrated stress and ground crack of coal pillar group is established,and the coupling criterion to avoid the coal pillar concentrated stress and realize the uniform surface sub- sidence is put forward,so the mechanism of reducing the stress concentration of coal pillar and realizing the uniform subsidence of the ground surface is revealed.