Strata gas enrichment rules under double mining influence of underlying protected seam

During mining process of underlying protected seam, strata are damaged twice under double mining influence, whose caving characteristics are different from that of ingle seam mining, and gas movement and enrichment status would be influenced. Taking underlying protected seam mining of Qingdong Coal Mine as research background, strata caving characteristics and gas enrichment laws under double mining influence are researched by use of similar simulation experiment and theoretical analysis. The results show that under the double mining influence of underlying protected seam, the strata in stope do large scale movement in a short time, and the secondary mining influence areas are formed periodically. Gas stably enriching in stope flows into the secondary mining influence areas, where gas enriches in a short time with periodical change. According to the research results, high level boreholes are carried out in No.828 working face of underlying protected seam in Qingdong Coal Mine for gas drainage. The secondary mining influence areas and gas enrichment laws are verified by through analyzing gas drainage concentration, and good gas control effect is achieved.