Deformation and air leakage mechanism of gob-side entry retaining and multiple collaborative prevention and control technology in thick coal seam

Abstract

In order to solve the problems of wall deformation mechanism of gob-side entry retaining, unclear air leakage flow field in goaf and poor gas control effect in thick coal seam, taking 20107 working face of Qincheng Coal Mine in Shanxi Province as the engineering background, mechanical modeling and theoretical analysis are used to study the influence of roof fracture position on stress concentration and propagation path in gob-side entry retaining. It is pointed out that when the fracture line is located outside the retaining roadway, the support stress can be effectively transferred and the pressure can be relieved. The calculation method of the key position of roof cutting by staged fracturing is proposed. By means of unit method measurement, the distribution law of air leakage flow field and gas concentration in goaf of gob-side entry retaining is revealed from two aspects of air leakage volume distribution in goaf and air leakage channel in gob-side entry retaining, furthermore, the multiple prevention and control technology of goaf gas in gob-side entry retaining is put forward, that is, the directional drilling staged fracturing roof cutting pressure relief-strengthening gas drainage advanced collaborative governance, weakening the transfer of roof pressure to avoid wall deformation and fracture air leakage, and improving the efficiency of goaf gas drainage. Silicate composite materials were used to spray and plug the existing wall crack development area ( at the junction of the roof and around the outer wall of the intubation ) to plug the air leakage channel of the roadway. With the optimization of the intubation parameters of the retaining roadway and the air volume ratio of the working face, the air leakage and gas emission in the goaf are further reduced, and verified by field investigation. The results show that : ①In 20107, the air leakage in 20107 goaf is mainly caused by the positive pressure leakage of the inlet air flow in the belt roadway, and the return air side is mainly caused by the leakage of high concentration gas into the gob-side entry retaining. The positive pressure air leakage in the 0-36 m section of the working face is 332.84 m3/min, accounting for 58.17%. The leakage air volume of the 36-108 m section of the retaining roadway is 408.45 m3/min, accounting for 87.09%. ②After optimization, the average gas drainage purity of directional drilling (fracturing hole+ pumping hole) in fracture zone is 7.46 m3/min, and the average gas concentration in gob-side entry retaining is gradually reduced from 0.59% to 0.34%. After fracturing and roof cutting, the deformation and fracture control of the retaining wall are greatly improved, and the efficient production of the working face is realized.

Keywords

• gob-side entry retaining
• goaf gas
• directional drilling
• roof cutting and pressure releasing
• spraying plugging