Analysis of reasonable width of water-proof coal pillars
In order to ensure the safe mining of fully mechanized caving face under the condition of wa-ter accumulation in adjacent goaf,the water-proof coal pillars between 2305 working face and 2303 goaf in Cuijiagou Coal Mine were studied as the background.The influence of water on coal body was ana-lyzed by physical and mechanical parameter test.The limit equilibrium theory is used to determine the width of the plastic zone on the side of the roadway,the softening modulus analysis is introduced to de-termine the width of the plastic zone on the side of the water accumulation goaf,and the Wilson coal pillar bearing theory was combined with the Bieniawski strength formula to determine the width of the elastic core zone;the plastic zone and stress distribution of coal pillars in 22～32 m were simulated by FLAC3D.The borehole stress meter and borehole peeper were used to monitor the stress and failure of the side coal pillar of the roadway.The results show that water has a great influence on the strength of coal,reducing cohesion and internal friction angle by 14%,compressive strength and tensile strength by 20%,and elastic modulus by 43%.The plastic zone on the side of the roadway is 2.74 m,the width of the plastic zone on the side of the goaf is5.01～6.60 m,the width of the elastic core area is17.10～17.48 m,and the minimum width of the waterproof coal pillar is 26.44 m.When the width of the coal pillar is greater than 28 m,the plastic zone on both sides of the coal pillar no longer changes.At this time,the width of the plastic zone on the side of the goaf is 6.00 m,and the width of the plastic zone on the side of the roadway is 2.00 m.The width of the plastic zone of the coal pillar on the side of the roadway is 2.4 m,which verifies the rationality of the theoretical analysis.
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