Study On The Movement Rule Of Thin Seam Overburden Strata With Hard Floor In Cilin Mountain Mine

Cilin coal mine belonging to Luan Mining (Group) Co. Ltd, the mine has beenmined for more than50years, the resource is verge of extinction, the residualrecoverable reserves of the No.3coal seam is only about1.50Mt, To ensure thesustainable development of the mine, the mining work of the9th thin seam must bedeployed as soon as possible. But there is no information about strata behaviorregularity of the9th thin seam by now, mastering the the law of the ground pressureand the the motion of overlying strata of the9101face can provide the basis in thesubsequent mining process for normal production, security management and supportselection, so this article should have a very important engineering application value.The the motion of overlying strata has been studied by using the methods ofpressure observation, theoretical analysis and numerical simulation.The results show that, sandy shale of5.57m thick over face roof can be seen thebasic roof, through averaging of field data and theoretical analysis to determine thatStope roof initial weighting step is34m, periodic weighting distance of13m. Directroof of limestone is belonged to hard roof, and its thickness is only0.77m, it can dropin the mining process. Dynamic load factor is1.25in the whole the observation period,roof pressure is not obvious. Analyzed as a whole, both initial pressure step andperiodic weighting step all showed that the roof weighting step of the middle isslightly larger than the roof weighting step of the end. Through analysing the fieldobservation data, the support resistance whose average value only about1960KN is57.7%compare by the rated support force，the working resistance of the period of thepressure is about the rated support force’s74.6%during all above data, the alarmworking resistance distributed in3032～3411KN account for8.07%of cyclic datastatistics. Considering face equipment of the "high-intensity, high-reliability" trendsthe hydraulic support of ZY3400/085/19type used in the face now is feasible.The boundary between caving zone and fractured zone has not been discoveredfrom the numerical simulation and it did not form "three zones"; Lower strata follow abottom-up sinking law. Advance support of20m is fully able to meet the requirementsof supporting roadway.The result has guiding significance for the safe production of9101mechanizedmining face.