Rationality and comprehensive unloading technology of deep high stress section coal pillars

Deep mines are generally faced with the problem of high stress in the coal pillars,which causes the serious deformation of the roadway. The main reasons for this are the unreasonableness of the coal pillars. In order to avoid the adverse effect of high-stress coal pillars on the roadway,taking the 2 -1 coal seam first mining area of the Hulusu mine,China,as a background,the deformation and failure range of the bottom slab under the concentrated load of the coal pillar and its influence on the roadway surrounding rock were studied based on the theory of plastic slip field and limit equilibrium theory. The results show that the 30 m section pillar reserved for Hulusu 2-1 coal seam currently has a greater influence on the floor rock under the effect of lateral support pressure,and its pressure failure zone covers the entire roadway floor area,which cause the roadway floor heave seriously. In order to effectively solve this problem,the “high and low” high-strength coal pillar comprehensive unloading technology was proposed. That is,the high-level “drilling,cutting,pressing” integrated technology cuts the stress transfer of the overlying rock,and the low coal seam small-bore blasting technology releases the accumulated load within the coal pillar. The results of field experiments show that the peak value of internal stress of coal pillars after unloading is from 22. 5 MPa to 15. 7 MPa,the pressure drops significantly,and the roadway deformation is effectively controlled.