Research On Pressure Relief Range Of Cross-Bed Hydraulic Punching In No.8 Coal Mine Of Hemei Coal Mine

No.8 Hemei Coal Mine is a gas prominence mine,mainly mining the Shanxi Group II₁coal seam,most of which is a single thick coal seam in the mine,with no protective seam to mine.The poor permeability of the coal seam and the small pressure relief range of the original extraction borehole largely affect the effect of gas extraction,so the purpose of eliminating the risk of protrusion cannot be achieved.Therefore,the main pressure relief and permeation measure during the construction process was hydraulic punching through the seam borehole.In this paper,a combination of theoretical analysis,numerical simulation and site investigation is used to study the pressure relief range of the perforated hydraulic punching in No.8 Hemei Coal Mine,which has high gas,low permeability and a single thick coal seam.Based on the existing research,the mechanism of hydraulic punching pressure relief and permeability increase is analysed;the research establishes a numerical model of hydraulic punching,and uses RFPA2D-Flow numerical simulation software to simulate and analyse the influence of factors such as vertical pressure,coal punching volume and coal body compressive strength on the pressure relief range of hydraulic punching,and also simulates the effective influence radius of hydraulic punching in the mine;according to the geological conditions of the mine,the gas emergence based on the geological conditions of the mine,a site investigation and analysis of the borehole was carried out using the attenuation characteristics method and the effective radius of influence of hydraulic punching was determined.The results show that:1.The pressure relief range of hydraulic punching increases with the increase of coal punching volume and vertical pressure,and gradually decreases with the increase of compressive strength of coal body.2.The numerical simulation results of hydraulic punching in the mine indicate that:the effective influence radius is 1.65m when no punching is done;the effective influence radius is 3.15m when the average coal punching volume is 0.41 t/m;the effective influence radius is 3.4m when the average coal punching volume is 0.9 t/m;the effective influence radius is 3.5m when the average coal punching volume is 1.3 t/m.3.The effective radius of influence is 3.4m,and the effective radius of influence is 3.5m for an average washed coal volume of 1.3t/m.3.The site inspection shows that the effective extraction radius and the average washed coal volume satisfy the relationship equation:y=1.81x+2.82（x<=1.3）.30 figures,11 tables and 75 references.