Study On The Pressure-relief Protective Area And The Feasibility Of Exploiting The Lower Protective Seam In Liyazhuang Coal Mine

Taking Liyazhuang coal mine of Huozhou coal electricity group Co.,LTD as theresearch object,according to its high gas and stress conditions in No.2coal seam,usingtheoretical analysis,field measurement,laboratory test and numerical simulation method,this thesis carries out the study on pressure-relief protective area and the feasibility oflower protective coal seam mining.The theory of protective seam exploitation is that itcan release the gas pressure and elastic potential energy of protected coal seam,andincrease the protected seam’s permeability.Gas flow in the protected seam becomeseasier.With gas desorption increasing and gas content decreasing,gas internal energy inseam is dropped.In order to analyze pressure-relief protective area and to determine thefeasibility with the exploitation of lower protective seam,this thesis researches on thedistribution regulation of strain and stress in the overlaying protected coal seam duringthe lower protective seam exploitation.Three stress distribution areas from open-off cutto stop line along strike are:concentrated area,released area and concentrated area.Alongdip,the distribution also obeys this regulation from upper roadway to lower roadway,butthe latter isn’t more uniform.The strain distribution regulation is compression,expansionand compression along both strike and dip.The max expansion occurs at the upperdistrict of the goaf roof. This thesis identifies that the protective area along both strikeand dip. It also researches on the moving regulation of pressurized water in No.6coalseam during the exploitation of lower protective seam, and finds that water inrushoccurs at open-off cut,stop line, rocky bottom when the width of waterproof coal pillaris respectively set at20m、40m、60m、80m、100m、120m、140m、160m. Then it evaluateswater inrush hazard in coal floor by water inrush coefficient method of effectivewater-resisting strata.The area under the level of289.28m in No.6seam is water inrushrisky zone of K2limestone water in Taiyuan group, and the area above it is threatenedzone. The whole exploitable area of the coal mine is water inrush threatened zone ofOrdovician limestone water.Finally, it identifies that the exploitation of lower protectivecoal seam is infeasibility from the aspect of preventing and curing water disaster.But inorder to ensure the sufficient use of energy, the coal seam can be exploited underpressure by floor grouting-strengthening.