Study On Strata Behavior Regularity Of Fully Mechanized Face In Hard Roof

Hard roof because of resistance to destroy the rock ultimate strength greatly. Inthe coal mining in the goaf can form a large area of hanging roof. The short term isnot easy natural caving. Usually weighting step distance and intensity are great causeface. The impact on the formation of face support. Pose a threat to the safety and highefficiency production. Therefore, accurately grasp the working face under hard roofpressure law is very necessary.The paper by Wang Cun mine of Datong Coal Mine Group8132working facemining background. Integrated theoretical analysis, laboratory research, numericalsimulation and site measurement method. The mining process of hard sandstone roofin fully mechanized workface are studied. The main conclusions are as follows:(1) The test of compressive strength of8132working face of coal sample RCis14.82MPa, Tensile strength Rtis0.92MPa, Cohesion C is1.18MPa, The angle ofinternal friction is44o. The test of compressive strength of roof sample RCis52.67MPa, Tensile strength Rtis4.84MPa, Cohesion C is3.82MPa, The angle ofinternal friction is45.3o. The test of compressive strength of floor sample RCis68.32MPa, Tensile strength Rtis3.87MPa, Cohesion C is6.07MPa, The angle ofinternal friction is40.9o.(2) By FLAC numerical simulation, With the advancing of working face, Abovegoaf appeared in pressure relief area. But in the cut hole and in front of the coal wallis always appear stress concentration region. And the vertical stress basicallysymmetrical distribution. The vertical displacement in the mining area central air thanon either side. And from the top down gradually. The goaf is compacted after initialpressure after.(3) The measured8132working face upper roof first weighting step distance is54.6m, In the lower part of the old roof first weighting step distance is57.1m, theaverage is55.85m. The level of Basic roof is IVa level, the basic roof pressureappeared very strong. Working face upper roof periodic weighting step distance is19.73meters, the old roof periodic central weighting step distance is23.74meters, thelower roof periodic weighting step distance is24.63meters, with an average of22.70meters. The working face roof activity tends to intense.