Research on pressure relief technology of deep and shallow hole combined blasting under retaining small coal pillar in double roadway excavation

In order to prevent and control the disaster of large deformation and strong ore pressure in the heading roadway under the arrangement of retaining small coal pillars in double roadway heading, the pressure relief technology of deep and shallow hole combined blasting was put forward based on the engineering background of Zhaozhuang coal industry.Through the research on the mechanical structure of the roof of the small pillar roadway and the mechanism of deep and shallow hole combined blasting, the correlation between the deflection of the gob roadway and the roof L of the goaf is revealed, and the location of the roof dip fracture is determined, so as to clarify the mechanism of the deep and shallow hole combined double-layer blasting to eliminate scour and protect the roadway and the mechanism of the deep and shallow hole combined guiding mechanics;The parameters of blasting scheme are determined by theoretical calculation and field test of articulated block.Engineering practice shows that:The pressure relief technology of deep and shallow hole combined blasting can weaken the energy storage attribute of hard composite roof media, optimize the triangle block structure of the goaf boundary roof, and reduce the accumulated energy density of the roof by about 4000 J at the same scale;The boundary roof of the goaf in 1313 working face collapsed in time after mining to reduce the squeezing effect of the roof on the coal pillar. The stress concentration coefficients at the measuring points at different depths of the coal pillar were 1.38 and 1.29, respectively, and the stress concentration degree was significantly reduced;The fan-shaped peaking results show that the fractures in the lower strata are obviously developed, and the upper strata are gradually damaged and fractured. Combined blasting in the roof inclination can reduce the length of the hanging roof of block B, destroy the articulated structure of the old roof, and weaken the slewing and sinking effect of the block.The maximum displacement of 13163 roadway roof and floor and two sides is 440 mm and 205 mm respectively. The blasting measures effectively restrain the roadway deformation, and no dynamic phenomena such as wall caving occur, achieving the goal of deep and shallow hole combined blasting.