Research On Dynamic Roof Structure In Shallow Seam Longwall Mining

Yushenfu Mining Area is the largest modern energy base of China in the beginning of21stcentury.It is necessary to study the ground behavior feature of tytpical shallow seem withbig minning height and the nearly shallow seam.The research has great guide meaning to thescientific mining of shallow seam working face.Dynamic roof structure in shallow seam longwall mining was further studied by field test,theoretical analysis,numerical simulation,and physical simulation.By field test,dynamicspecial law of ground behavior in shallow seam was revealed.The mining “arc”,“arc beam”and “arc pilliar” failure structure of thick sandy layer in typical shallow seam was obtained byphysical simulation. The dynamic “arc” failure and develop law and failure mechanism ofoverburden rock were disclosed. The “arc” failure model was set up and the equation was got,furthermore, the load transmiting rock and time factors in the first and period weighting intypical shallow seam were determined and the effect factors and changing law were furtherstudied. The support resistance formula of first and period weighting in typical shallow seamwere given and the reliability was verified by instances.Against the roof form of bedrock and clay in Yushenfu coal mine,the plastic and brittlesimulation model technique and ratio were developed. By simulation model test, the failurefeatures of main and sub-key strta tructure were controled,meanwhile,the big and small periodweighting load transmiting law was grasped. The “three zones” of overburden rock in shallowseam was studied and the mining cracks were classified.The downlink crack developmentmechanism was revealed by the “arc beam” model.By numerical simulation, the developmentlaw of stress arc in overburden rock of nearly shallow seam was obtained. The key andsub-key strata structure model was set up and the mutural effection relationship was studied.The criterion of key strata effecting the sub-key strata and the calculation method ofweighting distance were given.The big and small weighting mechanism was revealed. The support resistance formula in nearly shallow seam were given under the “masonry beams”and the “step beams” of sub-key stata.Research has guiding significance to the roof control and stent selection of Yushenfushallow seam coal mines, in the mean time, which has theoretical significance to rich the keystrata theory in ground control.