Study On Gas Control Conditions Of Gob By "One Hole With Multi-Purpose" Through Layer Drilling In Slate Roadway Of Guhanshan Mine

In mine gas control,the use of floor rock tunnels to drill through layers for pre-drainage,mining and drainage,and gas drainage in goaf,the so-called"one hole with multiple uses"is a subject actively explored by the academic community.Jiaozuo mining area is one of the most serious coal and gas outburst disasters in China.Because the coal seam is threatened by L₈ limestone water inrush,the floor rock roadway is arranged near the coal seam,resulting in the stability of the through layer drilling is greatly affected by mining.When the through layer drilling is used for pre-drainage,and the gas drainage is completed at the same time,the effect of continuous goaf gas drainage is not good.Therefore,the outburst mines in Jiaozuo mining area generally arrange high drainage roadway for goaf gas drainage.This kind of gas control method has the disadvantages of low utilization rate of Floor Rock Roadway Drilling and high cost of goaf gas control.Based on this,this paper studies the conditions of gas control in goaf by"one hole multi-purpose"type through hole in slate roadway of Guhanshan mine,aiming to improve the utilization rate of through hole in slate roadway of Guhanshan mine,reduce the cost of gas control in goaf,and provide new ideas for gas control in goaf.Taking the 1604 working face of Guhanshan coal mine in Jiaozuo as the research object,analyzes the lack of economy of gas control measures in the mine;uses the method of numerical simulation and field measurement to explore the effect of gas control in the goaf of 1604 working face;uses the method of numerical simulation to simulate the conditions of gas control in the goaf of floor rock roadway"one hole multi-purpose"cross layer drilling;uses the method of numerical simulation to obtain the conditions of gas control in the goaf;Using the method of field test,this paper analyzes the effect and influencing factors of"one hole multi-purpose"type through layer drilling in floor rock roadway for gas control in goaf.Finally,according to the geological conditions of Guhanshan mine,it puts forward the suggestion of"one hole multi-purpose"type through layer drilling for gas control in goaf,the main conclusions are as follows:（1）Guhanshan coal mine constructs a large number of floor rock roadway through layer boreholes,which are only used for pre drainage,with large engineering quantity and low utilization rate.Adopting high drainage roadway to control goaf gas is inconsistent with the gas control concept of"canceling high drainage roadway drainage"in"three cancellations and three strengthening"in Henan Province.Therefore,taking floor rock roadway through layer boreholes as"one hole multi-purpose"boreholes to control goaf gas can make up for the shortage Defects of gas control measures.（2）The goaf gas control standard of 1604 working face in Guhanshan coal mine requires that the pure gas drainage amount reaches 8m³/min.It is the most suitable to use the middle bottom drainage roadway through layer boreholes to extract gas from goaf.There are 21 boreholes in each group in 1604 middle bottom drainage roadway through layer boreholes.According to the simulation results of"one hole multi-purpose"borehole gas drainage in goaf,when the negative pressure is 10 kpa and the number of boreholes is 6,the gas drainage capacity is 7.80 m³/min,which can meet the requirements of gas drainage;when the negative pressure is 12 kpa and the number of boreholes is 4,the gas drainage capacity is 7.66 m³/min,which can meet the requirements of gas drainage;when the negative pressure is 14 k Pa and the number of boreholes is 4,the gas drainage capacity is 8.07 m³/min,which can meet the requirements of gas drainage Meet the requirements of extraction.（3）There is a high-efficiency area for gas extraction when using the"one hole for multiple purposes"type of through-layer boreholes to extract gas from the goaf.The field test is carried out on the bottom roadway in the middle of the 1604 working face.Under the experimental conditions of 16kpa negative pressure and 6 drilling groups,when the 6 drilling groups are distributed in the range of-20～-40 m from the working face,the pure quantity and concentration of drilling drainage are the highest,but the drainage quantity is still not enough to meet the requirements of goaf gas control,and the overall drainage effect is not good.This paper analyzes the reasons for the poor effect of gas control in goaf by using"one hole multi-purpose"cross layer boreholes in1604 working face,including:（1）the destruction of floor rock;（2）the poor air tightness of boreholes;（3）the influence of high drainage roadway;（4）the insufficient number of boreholes.（4）Due to the limitation of floor rock roadway in Guhanshan coal mine,the gas drainage function of"one hole multi-purpose"through layer drilling is restricted.The following measures are recommended:（1）optimize the drilling layout.At this time,the drilling plays the role of drainage.The specific method is to change the elevation angle of the drilling when opening,so that the drilling is drilled at a certain angle to the cutting direction,so that the time of the drilling affected by mining lags behind.When the drilling is not affected by mining,the goaf gas can be extracted,which is suitable for the working face without pre-drainage drilling layout;（2）the bottom drainage roadway is closed to extract the goaf gas.At this time,the role of drilling is to increase the permeability of rock strata and create gas flow channels.The reason why this drainage method can be adopted is that the floor rock roadway is close to the coal seam,the gas migration path is short,the floor rock roadway is in the plastic damage area of the floor,the cracks are developed,and the existence of drilling makes the gas flow easier.