Morphological characteristics and evolution law of plastic zone of mining roadway in extra-thick coal seam

Aiming at the serious damage of surrounding rock of mining roadway in extra-thick coal seam,the morphological characteristics of mining roadway plastic zone and their evolution law under the action of mining stress was studied by way of theoretical analysis and numerical simulation,taking haulage roadway of No.21141 working face in Qianqiu Coal Mine which locates at Yima Coal Field as the engineering background. The results showed that ①The shape characteristics of plastic zone were related to the bidirectional load ratio. Under different stress conditions,there are three different forms of plastic zone of circular roadway:round,oval and butterfly.②Under the influence of working face mining,the magnitude and direction of the principal stress field in the mining roadway of extra-thick coal seam will change. With the increase of the distance to the working face,the maximum principal stress increases sharply first and then decreases gradually along the axial direction of the mining roadway,and reaches its peak at 15 m away from the working face. The Angle between the maximum principal stress and x-axis increases gradually and approaches the vertical direction. The minimum principal stress reached the maximum at about 25 m away from the working face and then decreased slowly. ③Under the action of mining stress,the plastic zone morphological characteristics of mining roadway in front of working face will change. With the decrease of the distance to the working face,the plastic zone at the shoulder corner of the mining roadway expands to the depth,and its shape gradually evolves from irregular to butterfly shape. Moreover,the direction of butterfly blade in the plastic zone would be deflected with the maximum principal stress. The research results can provide a theoretical basis for the design of mining scheme of extra-thick coal seam and the determination of supporting parameters of mining roadway.〖JP〗