Impact hazard analysis and prevention research of square structure area in fully mechanized working face

Abstract

At present, the impact hazard analysis of fully mechanized working face is only carried out from a single geological structure or square effect factor. However, the mining conditions of rock burst mines are always changing, and the influencing factors are complex and diverse. Therefore, it is necessary to specifically analyze the impact hazard in the coupled area of geological structure and square effect in fully mechanized working face. Taking the 401111 working face of Hujiahe Coal Mine as the engineering background, the energy and frequency distribution characteristics of microseismic events of square structure area are obtained by microseismic network monitoring technology, and the impact hazard of square structure area is studied. The conclusions are listed as follows. ① The impact hazard is high in the square structure area, and the faults and folds in the area affect the continuity and deformation characteristics of the coal seam respectively, resulting in abnormal tectonic stress. ② The pressure of the overlying rock seam gradually transfers to the coal seam along with the excavation of the working face, and the concentration of static load in the area is significant. The square effect of the working face advancement process leads to frequent roof movement, resulting in a high level of concentrated dynamic load. ③ When the square effect and geological structure are combined, the concentrated static load in the coal body near the working face is at the highest level. The far-field concentrated dynamic load disturbance is the most frequent, and the potential hazard of regional impact under the coupling effect of the two is extremely great. In order to solve the problem of the impact hazards in the square structure area, specific prevention and control measures are taken for the three layers of the square structure area from top to bottom of the spatial dimension. ① The fracture of the thick hard roof will generate a high level of dynamic load, and pre-splitting blasting is carried out to reduce the connection between the roof and the adjacent goaf. ② The coal pillars and solid coal between the working faces are affected by the pressure of the overlying rock layer, and the static load concentration is high. It is proposed to implement large diameter drill holes to unload pressure and reduce the transfer of coal wall integrity support pressure to deep coal seams.③ It is proposed to implement large-diameter drilling + blasting pressure relief technology on the bottom plate to block the transfer path of the support pressure of the wall to the bottom plate and reduce the deformation of the bottom heave of the roadway. The results of engineering practice show that the prevention and control measures have good effect of pressure relief. The roof periodic weighting in the square structure area is shortened, which is basically below 15 m. The energy of the microseismic events at the working face is less than 104 J, and there is no large energy event. The proposed measures can provide reference for the prevention and control of rock burst in the same type of mine conditions.

Keywords

• fully mechanized working face; impact hazard; square structure area; square effect; dynamic load; static load