Abstract:
During the process of mining of the steep and ultra-close multiple coal seam groups, the roadway is affected by multiple mining, the regional stress environment is complex, the deformation and failure of the roadway is severe and the non-uniform characteristics are significant, and the support and maintenance are difficult. For such problems, taking the repeated mining roadway of the and ultra-close multiple steep coal seam 31233 transportation lane of Daichiba as the engineering background, the comprehensive research methods such as theoretical analysis, numerical simulation and field experiment are adopted to find out the evolution characteristics of surrounding rock stress environment at different locations of the roadway and the dis-similatory failure law of roadway surrounding rock under its influence, the special-shaped section which is beneficial to the convergence of plastic failure distribution of surrounding rock is designed, and the design method of non-uniform bolt ( cable ) support based on the alienation distribution law of plastic zone of roadway surrounding rock is proposed. The results show that under the influence of repeated mining of the steep and ultra-close multiple coal seam, the bidirectional principal stress around the roadway has a large difference, and the direction of the principal stress is deflected accordingly, resulting in the butterfly-shaped alienation characteristics of the surrounding rock of the roadway, such as non-uniformity and deflection of the maximum failure depth. The stagger position and cross-section shape of the roadway determine the failure form and scope of the roadway, and the stagger distancet directly affects the dissimilation distribution and scope of the plastic zone of the surrounding rock, and the existence of hard rock causes local annihilation of the plastic zone. When the position of the roadway is staggered to more than 17 m, the stress environment around the roadway tends to be stable, and there is no obvious change in the plastic size and shape of its surrounding rock. The internal dislocation position is greater than the distance, which is most favorable for the stability of the surrounding rock of the roadway. The unilateral span size of the roadway section determines the depth of plastic failure on its side. When the roadway section is a polygonal special-shaped section, the convergence degree of plastic distribution of surrounding rock is significant. In the design of roadway section, the longest side of roadway should be located on the side of hard rock stratum and try to avoid the direction of maximum failure depth, so as to make full use of the annihilation characteristics of plastic zone of hard rock stratum and avoid the excessive expansion of butterfly leaves in plastic zone of roadway surrounding rock. Therefore, the geometric characteristics of the section of the special-shaped roadway with the condition of steep coal seam can be fully utilized. Based on the dissimilation distribution law of the plastic zone of the surrounding rock of the roadway and the distribution characteristics of the reasonable anchorage layer, the non-uniform bolt (anchor cable ) support design can be carried out, which can effectively guarantee the support force of the bolt (anchor cable ) and ensure the overall stability of the surrounding rock of the roadway. At the same time, the industrial test was carried out in 31233 headentry. Before the influence of severe mining, the monitoring station of deep displacement of roadway roof and anchor cable support force was set up. During the monitoring period, the total deformation of roof deformation was controlled within 100 mm, the anchor cable support force was stable, and the overall control effect of surrounding rock was better.