Study On Coal Pillar Crack Evolution And Air Leakage Characteristics Of 509 Working Face In Madiliang Coal Mine

This article is based on the on-site geological production conditions of Madiliang Coal Mine,combined with the mine’s fire prevention and extinguishing needs,and conducts laboratory basic parameter measurement and on-site measurement of the evolution law and air leakage characteristics of the 20 meters protective coal pillar crack between the 507 and 509 working faces.Scientifically evaluate the mechanical parameters and spontaneous combustion characteristics of coal seam 5#based on the results of coal rock sample collection and testing,as well as the experimental results of spontaneous combustion characteristics of coal seam 5#;Using PFC^3D software to simulate the development and connection trend of internal cracks in a 20 meters coal pillar under the influence of dynamic mining pressure in the 509 working face;Based on the experimental results of CT scanning of the evolution characteristics of coal pillar cracks and the on-site measurement of coal pillar air leakage characteristics,the evolution law and air leakage characteristics of the 20 meters coal pillar cracks in Madiliang Coal Mine have been clarified,and targeted comprehensive fire prevention and extinguishing measures have been proposed.Firstly,on-site collection of coal and rock samples from the 509 working face of Madiliang Coal Mine was carried out.The laboratory completed mechanical parameter testing of the coal and rock samples,as well as temperature rise oxidation testing of the coal samples.The key mechanical parameters for the evolution of coal pillar cracks and the natural combustion index gas in the goaf were obtained.Secondly,based on the influence range of the forward moving support pressure in front of the working face and its contribution rate to the development of coal pillar fractures,combined with the PFC^3D numerical simulation results,the coal pillar in front of the working face is divided into:0-10 meters mining impact fracture penetration area;10-30 meters peak stress crack development zone;The upper working face 30 meters away affects the fracture occurrence area.The numerical simulation results indicate that a large area of interconnected cracks and air leakage channels are formed in the coal pillar within the crack area of 0-10 meters.Finally,a plan was designed to lay the bundle pipes in the goaf of the 507working face within a 20 meters coal pillar,achieving on-site monitoring of the air leakage characteristics of the 507 working face goaf coal pillar and the distribution of the flow field in the goaf during the mining period of the 509 working face.The variation characteristics of oxygen concentration in the goaf of the 507 working face were obtained from the gas composition detection system of the coal pillar bundle tube,especially in the area 1 to 10 meters away from the working face where the coal pillar is affected by the advanced moving support pressure.This further demonstrates the internal correlation between the coal pillar leakage area and the dynamic pressure of the working face during mining.Based on the natural combustion characteristics of the 5#coal seam,the evolution law of coal pillar cracks,and the on-site measurement results of air leakage characteristics,a comprehensive fire prevention and extinguishing measure combining yellow mud grouting,nitrogen injection,and spraying inhibitor has been developed for the 509 working face,providing a guarantee for the safe and efficient mining of the 509 working face.The paper has 56 figures,25 tables and 60 references.