Research And Application Of Horizontal Deep Hole Advanced Pre-splitting Blasting Technology For Hard Rock Wall Inside Fully Mechanized Mining Face

The underground fully mechanized mining face will encounter complex and variable geological structure areas during the process of advancing.The hard rock walls,subsided columns,faults and intrusive rock masses inside the working face will hinder the normal advancement of the fully mechanized mining face.The coal cutter moves through the working surface in a forced manner,and the fully mechanized coal cutter tool will be seriously worn,which not only reduces the recovery efficiency,but also affects the normal production of the working face,and increases the mine production cost.In order to allow the fully mechanized mining machine to pass through the geological structure area,the blasting method is considered to destroy the integrity of the rock wall.If the blasting work is directly carried out on the working face,the pre-fractured rock wall may cause serious damage to the fully mechanized mining equipment and affect the normal production of the working face.Therefore,the method of testing the horizontal ultra-deep hole blasting weakened rock wall in the material lane or the return air lane is considered,and the hard rock wall is treated without affecting the normalmining of the working surface and destroying its integrity,ensuring the mining equipment passes through the affected area of the rock wall normally.The 8308 working face of Wangping Coal and Electricity Group encountered hard rock wall in the process of mining,which hindered the normal production of the working face.This is the background of engineering research.Combined with the basic theory of rock blasting weakening and numerical simulation technology,the blasting scheme was designed and implemented on site.According to the specific geological conditions of the working face of Wangping Coal Mine,the physical model is built using simulation software.The optimal hole spacing of the blasthole under the coupled and uncoupled charge structure,the optimal distance between the rock wall head blasthole and the coal-rock interface,and the uncoupling coefficient of the charge under the uncoupled charge structure are numerically simulated.Concluded as follow:(1)Analyze the action process of explosives after blasting inside the rock,and explore the formation mechanism and influence range of each blasting zone;(2)The failure mechanism and mechanical response of rock under dynamic and static loads and the propagation process of explosive stress wave are analyzed.The difference between rock failure mode and staticload failure under explosive dynamic load is discussed;(3)Using ANSYS/LS-DYNA,the reasonable hole spacing of the blasthole under the coupled and uncoupled charge structure,the reserved distance from the nearest blasthole and coal-rock interface of the coal wall,and the uncoupling under the uncoupled charge.The numerical calculation of the coefficients shows that the distance between the two holes of 1.0m under different charge structures(coupling and decoupling)is a reference value;the decoupling index under the decoupled charge structure is 1.7;The reserved distance between the nearest blasthole and the coal rock wall is 0.8m;(4)After the 8308 working face of Wangping Coal Mine was implemented with the simulation results as the reference optimization,the fully mechanized coal cutting machine passed the affected area of the rock wall.