Investigating coal pillar size in district sublevel and regional surrounding rock controlling in inclined extra-thick coal seam
To identify the appropriate coal pillar size in district sublevel of gob-side entry driving in fully mechanized caving face in an inclined extra-thick coal seam,the 11503 fully mechanized caving face in Mengjiayao Coal Mine was chosen as the engineering background.A mechanical model of"large and small structure"in an inclined coal seam working face was developed,considering the strata struc-ture following the collapse of main roof.The theorem defining the low stress field range suitable for loca-ting the small structure was derived,and the conditions necessary and sufficient for the instability catas-trophe of coal pillar in district sublevel were analyzed using"cusp catastrophe"theory.Moreover,the stress of coal pillars with different sizes and the deformation law of surrounding rock was simulated by FLAC3D.The research findings indicated that shear failure was the primary internal failure mode in coal pillars due to the inclination angle of the coal seam and the rotary-extrusion of key blocks in the main roof.The failure region was mainly concentrated in the upper portion of the coal pillar,near the gob area.With the increase of the coal pillar width,small-range of pressure in overlying strata of gob-side entry driving gradually transferred from intact coal side to coal pillar side.After considering the changes in stress field,displacement field,and plastic zone,the reasonable size of coal pillar was determined to be 15 meters.By analyzing the stress distribution and evolution characteristics of surrounding rock in the gob-side entry at various mining stages,different surrounding rock control schemes were proposed.Engi-neering practice has demonstrated that a coal pillar with a width of 15 m,along with the corresponding surrounding rock control scheme,can meet the stability requirements of roadway.
pillar size in district sublevelcatastrophe theoryextra-thick coal seamregional sur-rounding rock control
万方数据
维普
