Study on temporal and spatial distribution and treatment of “U” ventilation gas in gob-side entry retaining

Abstract

Aiming at the problem of gas accumulation in upper corner and return air roadway of single U type ventilation mining in early stage of gob-side entry retaining in Mingxin Coal Mine, the mathematical equation of gas convection and diffusion is established and a strong coupling physical model is built. In the stable stage of ventilation, the space-time distribution of gas under the conditions of high-level borehole extraction and pure air exhaust is studied and verified by field practice. The study results show that when the mining distance is 20 m, the flow field in the goaf forms the complex distribution of “B” and “D”, which causes the peak of gas volume fraction in the working face. There are two-fifths of the goaf area along the goaf side forms an interception influence area, and one-seventh of the goaf area forms an triangular return area under the condition of extraction, which indicates that the extraction weakens the trend of the goaf flow line closing to the upper corner of the goaf side and the goaf flow line developing to the goaf side of the goaf; under the condition of extraction, the starting point of gas volume fraction rise in the direction of goaf in upper corner is 4.7 m behind that of pure air exhaust, and the peak value of gas volume fraction in upper corner, average value of working surface and average value of return lane decrease 86%, 69% and 37.7% respectively. Field practice shows that the smooth area of gas volume fraction in return lane before and after treatment is extended by 60 m, and thepeak value of gas volume fraction in upper corner and return lane decreases by 21.7%.

Keywords

• gob-side entry retaining
• flow field
• bilateral goaf
• gas accumulation
• spatial and temporal distribution