The Optimization And Research On The Reasonable Size Of Coal Pillar With Fully Mechanized Caving Mining In Large Dip Angle And Thick Coal Seam

The coal seam is divided into gently inclined, inclined and steeply inclined according to the coal seam angle in China, but there is no exact definition of the large dip angle coal seam, the domestic scholars think it refers to the coal seam with35°～55°ngle according to the natural repose angle of caving gangue slip(35°) and the hydraulic support maximum angle of longwall face along strike mining(55°). With the continuous production of coal seam with good occurrence conditions, large dip angle coal seam has gradually become the main minable seam in many mines, but because of the influence of dip angle, the coal seam overburden rock structure is complex. Under the influence of the stope lateral support pressure, coal seam dip angle, coal seam strength and roof characteristics, especially under the specially thick coal bed geological conditions, section coal pillar stability in large dip angle and specially thick coal seam is very different from the flat seam and gently inclined coal seam. So the study on the breaking structural characteristics of section coal pillars and overburden rocks, the coal pillar vertical stress distribution law and the stability of coal pillar under the large dip angle special thick coal seam geological condition has great significance to the mining theory and the field practice.Through the field research and theory analysis, the paper sums up the "asymmetry" of the overlying strata caving forms and the "three hinged arch" structure formed along the stope slope direction in the large dip angle coal seam when using strike long wall method; affected by this structure, the "timeliness" of pressure change of working face is shown in the strata behaviors characteristics.Through the establishment of small hinged structural mechanics model composed of the A,B and C rocks formed by breaking in inclination of section coal pillar overburden rock during strike to long wall mining, using the theory of masonry beam, the paper analyzes the equilibrium conditions of bond-beam rock slipping and rotary deformation instability that influence the stability of section coal pillar.On the geological condition of No.5large dip angle coal seam in Meng Jiayao Coal Mine of ShanXi Lu’an Group, using the limit equilibrium theory, the paper concludes that the reasonable width of section coal pillar is the sum of plastic zone width on both sides of coal pillar and center elastic area coal critical dimension. Meanwhile, the paper analyzes that weal plane is in the coal pillar and the time correlation of coal pillar deformation, concludes that the measures should be taken and the minimum time calculation formula to keep coal pillar stability when the weak plane is in section coal pillar. Using the finite difference method, the paper studies the different wide section coal pillar yield failure situation and vertical stress distribution law when is disturbed by roadway driving, first mining and secondary mining during the longwall working face along strike roadway driving, upper section working face mining and lower section working face mining, and concludes the different wide section coal pillar abutment pressure distribution law curve when affected by upper and lower section working face mining. And through comparison and analysis, the paper draws a conclusion that when the width of section coal pillar is25.0m it can remain stable.