Study on mineral and rock characteristics of roof and floor of water-rich coal seam in Balasu Mine Field

The water-rich problem of coal seam in Jurassic Coal Field in Northern Shaanxi Province is very special, which seriously affects the safety of mine production. The X-ray diffraction, thin section analysis, scanning electron microscopy and other experimental studies are carried out on the mineral and rock characteristics of the roof and floor surrounding rock of No.2 water-rich coal seam in Balasu Coal Mine, Yuheng Mining Area（northern）. Combining with the experimental results of other non-water-rich coal seams, the particularity of rock characteristics of rock minerals in the top and floor surrounding rocks of No.2 water-rich coal seam in Balasu Coal Mine is found. The results show that the lithology and mineral composition of water-rich coal seams are similarities and differences. The sandstones of Zhiluo Formation and Yan’an Formation in the roof of No.2 coal seam of Balasu Coal Mine and Dahaize Coal Mine are mainly feldspar sandstone, feldspar lithic sandstone and lithic feldspar sandstone, and their mineral compositions are mainly quartz, feldspar and clay minerals. However, from the perspective of the occurrence of rock deposits in the top and bottom of coal seam, the relative occurrence content of clay minerals in the water-bearing strata of No.2 coal roof of Balasu Coal Mine is relatively low, so it is relatively difficult to form cemented bodies that plug the pores of rock strata. According to the occurrence state of pyrite, it can be concluded that the groundwater fluidity and water richness of Balasu Mine Field are better in the original sedimentary environment. Meanwhile, from the analysis of mineral contact characteristics, it is found that compared with Zhiluo Formation, Yan’an Formation sandstone has relatively poor water richness. Moreover, there are traces of compaction in the floor strata of coal seam, which is not conducive to the further infiltration of pore water. The resulting difference in water richness is obvious. By comparing the test results of surrounding rock of the No.2 coal seam in the adjacent Dahaize Mine Field, the surrounding rock of the No.2 coal seam in Balasu mine field may provide environmental conditions and recharge capacity for water filling, and reveal the non-water-rich surrounding rock environment characteristics of the No.2 coal seam in Dahaize Mine Field. The research ideas, methods and results can provide basic basis and theoretical reference for the research on the formation mechanism and occurrence law of water-rich coal seam in Yuheng Mining Area（northern）.