Research On Bearing Characteristic And Load-bearing Effect Of Composite Bolt-rock Bearing Structure In Roadway

With the continuous increase of mining depth,the deep mining conditions become more and more complicated,which are attributed to the development of joint fissures,loose structure and large failure range on surrounding rocks in the deep roadway.The roadway support design with full considerations to the characteristics and loading effect of composite bolt-rock bearing structure is an effective solution to the above problems.A systematic analysis on the mechanical mechanism of loading effect of the composite bolt-rock bearing structure,stability and mechanical characteristics of surrounding rocks in roadway based on the loading effect of the composite bolt-rock bearing structure,influencing factors of bearing capacity and structural features of the composite bolt-rock bearing structure was carried out in the present study.Through the research,mainly achieved the following results:(1)The loading mechanical model of the composite bolt-rock bearing structure is constructed.According to analysis,the loading strength of composite bolt-rock bearing structure is proportional to supporting strength of the anchor,internal cohesion of the composite bolt-rock bearing structure and the vertical stress growth rate.In addition,the loading strength of composite bolt-rock bearing structure is positively related with the internal friction angle and thickness(b)of the composite bolt-rock bearing structure,but it is negatively related with width and radius of the roadway.These not only interpret the loading mechanics of the composite bolt-rock bearing structure,but also disclose the relations of loading characteristics of the composite bolt-rock bearing structure with the minimum support strength and maximum allowable deformation of the roadway.Moreover,influences of characteristics of the composite bolt-rock bearing structure on stability of surrounding rocks in the roadway as well as reasons of stable roadway under small supporting strength are concluded.(2)Based on the loading effect of the composite bolt-rock bearing structure,the Mohr-Coulumb strength criterion is corrected using the Levy-Mises constitutive relationship with full considerations to problems in solving of the Kastner equation.The corrected Mohr-Coulumb strength criterion explains the influences of stress of primary rocks,internal friction angle of rocks and uniaxial compressive strength on stress threshold of the primary rocks,radius of plastic region and stress distribution on surrounding rocks in the roadway.For a specific working condition,the international friction angle applicable to the correction of Mohr-Coulumb strength criterion has an extreme value.According to the corrected Mohr-Coulumb strength criterion,the radius of the plastic region is small and the tangential stress peak is high,which determines the stronger concentration of internal tangential stress in the plastic region.Consequently,roadway is easier to develop deformation instability.The Mohr-Coulumb strength criterion which is corrected based on the Levy-Mises constructive relation is more applicable to high-stress field conditions.(3)The variation law of displacement on the composite bolt-rock bearing structure surface and stress at the measuring points in different stress stages in the different sections of roadway is studied by the two-way three-side adjustable analog simulation test device proposed by the research team.In the same time,the loading characteristics of the composite bolt-rock bearing structure in the slow loading stage,accelerated loading stage and the post-peak loading stage are acquired.The deformation failure features and its evolution laws of the composite bolt-rock bearing structure are disclosed.(4)A numerical simulation study based on the single-factor control method demonstrates that the thickness of the composite bolt-rock bearing structure is positively related with the length of anchoring rod(such positive effect becomes unobvious after reaching a certain length of the anchoring rod),and it is negatively related with width of roadway.The stronger preloads and smaller space between anchor rods are conducive to the effective formation of composite bolt-rock bearing structure and thickening of the support.Given the smaller diameter of the anchor rod,the pressure stress at the tray is more concentrated,which is disadvantageous for further diffusion of pre-stress.Based on the stability analysis of roadway,support parameters and width of roadway present consistent influences on the structural characteristics and loading characteristics of the composite bolt-rock bearing structure.Finally,the internal correlation between structural characteristics and loading characteristics of the composite bolt-rock bearing structure is concluded.(5)Based on the bearing effect of composite bolt-rock bearing structure,roadway support scheme optimization and support effect was put forword together with stability evaluation method of roadway,and successfully applied in Huaibei mining Limited by Share Ltd Luling Coal Mine.Figure[66] Table[15] References[161].