Hard Roof Presplitting Blasting Roof Cutting Pressure Relief Mechanism Of Roadway Protection Research In Jianda Mine

In order to alleviate the difficulty of mining and replacement in Jianda Mine,when carrying out mining work in Working Face 110104,the next adjacent working face mining roadway is arranged in advance.Among them,the 110110 haulage roadway undergoes multiple dynamic pressure actions,and the roadway presents strong rock pressure problems.In view of this practical engineering problem,this thesis adopts theoretical analysis,laboratory experiment,numerical simulation,industrial test and other research methods,and from the perspective of hard roof conditions and presplitting blasting roof cutting pressure relief,studies the main contents of the hard roof collapse law,mechanical analysis of roof cutting pressure relief,presplitting blasting cracking mechanism,key parameters of roof cutting pressure relief,and draws the following conclusions:(1)According to the geological conditions of 110104 working face,the mechanical model of hard roof is established,and the collapse law of hard roof,the mechanism of roof cutting pressure relief and the bending deformation characteristics of roof rock beam are analyzed.The study found that the smaller the deflection of the roof rock beam,the stronger the support structure composed of crushed gangue in the goaf,and the better the effect of presplitting blasting on roof cutting pressure relief.(2)Through theoretical analysis and LS-DYNA numerical simulation,the conditions for crack generation,propagation process,and spacing between blasting holes in presplitting blasting were studied,and the mechanism of presplitting blasting cracking was revealed.The appropriate spacing between blasting holes was determined to be 800 mm.The study found that,under the action of a charging device,the explosive gas and stress waves generated by presplitting blasting mainly propagate along the charging direction,reducing the meaningless diffusion in the other directions,effectively reducing the damage caused by blasting to the surrounding rock,and making it more conducive to the penetration of cracks between adjacent blasting holes.(3)Establish a UDEC numerical model for presplitting blasting roof cutting pressure relief,simulate and study the structural characteristics of roof surrounding rock,the stress evolution law of both sides of the roadway,and the displacement evolution law of the roadway roof under different roof cutting angles and heights,and determine the most suitable roof cutting angle and height as 10 ° and 15 m.The study found that the main impact of the roof cutting angle is the bearing capacity of the hard roof caving gangue on the roof cutting cantilever structure,while the main impact of the roof cutting height is the hard roof caving situation and the filling effect of the goaf.Only by selecting appropriate key parameters for roof cutting pressure relief can the smooth collapse of hard roof be ensured,and the effect of presplitting blasting roof cutting pressure relief for roadway protection can be achieved.(4)A pre splitting blasting roof cutting and pressure relief on-site test was conducted in the 110104 return air roadway,and the support plan for the 110110 transportation roadway was redesigned to adapt to the roof rock structure after roof cutting and pressure relief.Through drilling and observation,the observation results showed that the cracks between adjacent blasting holes developed well after the top cutting and pressure relief.Field experiments further proved the feasibility of pre splitting blasting for top cutting and pressure relief roadway protection.