Study of the Evolution of Water-Conducting Fracture Zones in Overlying Rock of a Fully Mechanized Caving Face in Gently Inclined Extra-Thick Coal Seams

To study the caving of thick hard overburdens and evolution water-conducting fracture zones in fully mechanized top-coal faces gently inclined extra-thick coal seams, we comprehensively analyzed 8103 working face Beixinyao Coal Mine. We investigated to characteristics overburden faces, information internal structure overburden, development heights “two zones” after mining. Our research methods included those similarity simulation experiments, such as use microseismic monitoring systems, numerical simulations, theoretical analysis, engineering practice. The results showed that overlying strata generally experienced stages roof caving, crack formation, delamination, development, surface subsidence. Due influence movement mining, separation layer an process called “emergence-development-closure”, where height envelope increases with advancing face. When full mining was achieved, stable, range zone 100–120 m, which is consistent envelope. Most events occurred near zone, formed area concentrated energy density. In our simulation, distribution field characterized by a “bridge arch”. model middle goaf higher than at both ends face, deformation obvious. value event reaches 108.708 J, cracks are produced, these gradually penetrate form zones. Engineering practice 98–123 provide scientific basis for water prevention control.