Study And Application Of Deep Hole Pre-splitting Technology In The Rock Protective Seam Working Face Of Pingmei Thirteenth Mine

The mining of rock protection layer will face the problem of working face passing through sections,which can lead to difficulties in cutting hard rock sections and high equipment loss during the mining process of the protection layer.This thesis is based on the engineering background of the 13070 rock protective layer working face in the13 th Coal Mine of Pingdingshan Coal Industry Company.The research methods of theoretical analysis,numerical simulation,and on-site engineering tests are used.Analyze the geological conditions of the rock protection layer and master the basic physical and mechanical parameters of hard rock in fault zones.Based on the joint rock breaking mechanism of explosive stress wave and explosive gas,a reasonable borehole diameter and borehole spacing have been determined.A deep hole pre-splitting blasting technology scheme was proposed and blasting practice was carried out on-site.The development of cracks on the hole wall is obvious through observation with a peep instrument,and the pre cracking effect of blasting is significant.The main research results are as follows:(1)Analyzed and mastered the engineering geological characteristics of the 13070 protective layer working face in the 13 th Coal Mine of Pingdingshan Coal Industry Company.There are two fault zones at a distance of 720 meters and 1100 meters from the stop mining line.These faults are all normal faults,with an inclination angle of about 60 ° and an elevation difference of 0.8-6 m.The basic mechanical parameters of sandstone in the fault area of the protective layer have been clarified.The compressive strength and tensile strength are 105.1 MPa and 2.7 MPa respectively.The internal friction angle of the rock is 37 °,and the cohesive force is 4.2MPa.(2)Analyzing the rock breaking mechanism of the combination of explosive stress wave and explosive gas,it was calculated that the fracture radius under blasting action is between 0.7 and 1.2 meters.Numerical simulation was conducted based on geological conditions,and the damage characteristics of rocks under blasting were mastered.It was found that the radius of complete damage to the rock is 0.3 m.The farther away from the explosion center,the smaller the damage value of the rock.When the rock mass is 1.4 meters away from the explosion source,the damage factor of the rock is 0.(3)Establish a numerical model using LS-DYNA dynamic analysis software to analyze and compare the effects of blasting parameters such as hole spacing and hole diameter on blasting effectiveness.The results indicate that the range of the surrounding rock crushing zone on the borehole wall decreases with the increase of the borehole diameter,while the radius of the fracture zone gradually increases.The larger the spacing between blast holes,the higher the energy loss along the path,the smaller the rock stress in the center of the blast hole connection,the smaller the crack propagation and penetration,and the smaller the range of rock fragmentation.(4)Based on the basic overview of the 13070 rock protection layer working face in the 13 th Coal Mine of Pingdingshan Coal Industry Company,advanced pre-splitting deep hole blasting operations were carried out in the air and machine tunnels of the protection layer.The depth of the blasting holes in the machine and air tunnels is 80 m and 60 m,respectively.The sealing length of the blasting holes is 20-27 m,the hole diameter is 94 mm,and the spacing between the holes is 2 m.The peeping results of deep hole blasting show that the fracture development of surrounding rock is obvious.The thesis has 51 figures,22 tables,and 85 references.