Effective Anchoring Mechanism And Application Of Layered Roof In Coal Measure Roadway

The stability control theory and technology of surrounding rock in coal measures layered roof roadway have been developed.Especially with the popularization and application of bolt support technology,the concept of support-surrounding rock joint bearing has been widely accepted.At the same time,due to the typical layered characteristics of the coal seam roof,the existing theory does not have a deep understanding of the anchoring mechanism between the bolt support structure and the’bolt-surrounding rock’.This thesis focuses on the key scientific problem of how to realize effective anchoring of bolt in layered roof roadway of coal measures.Taking the anchorage body system composed of’bolt-C40 concrete’as the research object,the evolution law of internal stress field of bolt anchorage body under different conditions of bolt pre-tightening force,length,density and borehole inclination angle is studied by means of physical model experiment and numerical simulation.On this basis,the mechanical properties of anchorage body under effective anchoring state are studied,and the technical scheme of II8₂24N machine roadway support in Renlou Coal Mine is evaluated and analyzed.The interaction between pre-stressed anchor and surrounding rock is studied by establishing a theoretical mechanical model,and the influence trend of key influencing factors is obtained.It is found that after the pre-tightening force is significantly increased,the anchor force forms the effective support stress range.The increase of bolt density has obvious effect on improving the overall support stress and achieving coupling support.The support stress reaches the maximum value at the initial position of the anchorage section,and then gradually decays rapidly.There is a significant positive correlation between the preload and the peak support stress.The increase of the anchorage length will lead to the stress peak position moving forward.The influence of pre-tightening force and anchorage density on the effective anchorage of anchorage body is obtained by physical test.The results show that under the action of certain pre-tightening force,the internal stress of anchorage body increases with the increase of pre-tightening force.Under the action of group anchor,the effective anchorage effect can be produced by the nonlinear superposition of adjacent anchors on the internal stress of anchorage body.The numerical simulation study reveals the mechanical effect of surrounding rock support under different anchorage modes.The larger pre-tightening force is used to retain a certain free segment length,or the length of the bolt is increased and the spacing of the bolt is reduced to facilitate the diffusion of the pre-tightening force of the bolt in the surrounding rock,thus forming an effective anchorage support structure.In the case of large spacing of anchor cables,increasing the preload and shortening the length of anchor cables appropriately can improve the control effect of surrounding rock.Based on the effective anchoring effect,the advanced support technology of the roadway during the mining of the Ⅱ8₂24N working face in Renlou Coal Mine was studied,and the stability evaluation system of the surrounding rock of the two roadways in the mining face was established,which reduced the labor intensity of the workers,improved the construction quality,and effectively controlled the deformation of the roadway surrounding rock under the influence of mining.