| After many years of research,it is found that in the actual production,narrow coal pillar can be left to protect the roadway,or even not to protect the coal pillar,which can also meet the needs of safe production,improve the recovery rate,and avoid the waste of resources.However,there are many problems in theory and engineering application,such as local roof leakage and large deformation of narrow coal pillar in gob side entry driving and mining process,which even threaten the safety of mine production;As well as the specific location of gob side entry and the reasonable size of narrow coal pillar.Based on the analysis of the geological production conditions of Tiefeng mine,combined with the monitoring data of mine pressure,this paper uses theoretical analysis,numerical simulation and other methods to study the mine pressure behavior law of gob side entry driving in Tiefeng mine and the reasonable reserved size of narrow coal pillar for roadway protection,so as to reduce the impact of mine pressure behavior on the production of working face and reduce the waste of coal pillar resources in working face section,It provides reliable experience for mining under similar conditions in the future.(1)According to the mine pressure observation results of fully mechanized caving face in Tiefeng mine,the mine pressure distribution law and the side overburden structure of gob side roadway when retaining narrow coal pillar for roadway protection are analyzed and calculated theoretically,and the theoretical value of retaining size of narrow coal pillar for roadway protection is 6.38 m.(2)Numerical simulation is used to analyze the mine pressure distribution law and deformation and failure characteristics of narrow coal pillars with different sizes.The vertical stress of narrow coal pillars and the surrounding roadway increases and transfers with the increase of the width of narrow coal pillars.The stress concentration factor in narrow coal pillars of roadway protection presents the change law of gradually decreasing at first and then increasing.When the width of narrow coal pillar is 7m,the range of plastic zone of roadway roof and plastic zone of narrow coal pillar is obviously smaller than that when the narrow coal pillar with smaller width is reserved for roadway protection,and the range of plastic zone of roadway roof is also reduced accordingly.When the width of narrow coal pillar is increased continuously,the area of plastic damage of narrow coal pillar and surrounding rock of gob side entry is reduced compared with that of 7m narrow coal pillar.(3)Under the influence of mining,the stress of surrounding rock and narrow coal pillar of gob side entry appears peak at 15 m in front of the fully mechanized top coal caving face with narrow coal pillar.The peak value of the leading abutment pressure in the middle of the fully mechanized top coal caving face is about 5m in front of the coal wall,and the affected area is about 50 m.In the area of 5m ? 10 m in front of the working face,the plastic damage range of the gob side roadway and the side of the solid coal is large,so effective measures must be taken to strengthen the support to ensure the normal production of the working face;In the range of10m-15 m in front of the working face,the plastic damage of the roof and solid coal wall of the gob side entry is reduced compared with the range of 5m-10 m,but the support still needs to be strengthened.Finally,compared with the results of field monitoring data,combined with the results of theoretical analysis,numerical simulation and comprehensive analysis,the research shows that the reasonable width of narrow coal pillar is 7m. |
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