Unified Solution Analysis Of Elastoplastic Mechanics Of Deep Buried Circular Roadway Under Multi-factor Influence

The environment of the underground buried roadway is complex,and the distribution of stress,strain,displacement and plastic zone radius is very important in the design process.In order to facilitate the research,the circular roadway problem is regarded as a plane strain problem,a unified solution of the circular roadway under the influence of multiple factors is established,and the stress,strain,displacement and plastic zone distribution law of the surrounding rock of the roadway are analyzed,and the calculation results are obtained by theoretical derivation and numerical simulation,and the results of on-site monitoring are compared and analyzed,and the conclusions are as follows:（1）Taking into account various factors such as rheology,different strength criteria,strain softening,intermediate principal stress,and dilation,four-quadrant and three-quadrant models of circular tunnels were established.An elasto-plastic constitutive equation was introduced to consider the influence of various factors on circular tunnels under plane strain conditions.By satisfying the displacement and stress continuity conditions,analytical solutions for the stress,strain,displacement,and plastic zone radius of the four-quadrant and three-quadrant models of the surrounding rock of the tunnel were obtained.（2）Based on the unified strength theory of double-shear and triple-shear,the unified solutions of double-shear（four zones）,double-shear（three zones）,triple-shear（four zones）and triple-shear（three zones）are obtained respectively.The difference between the four-zone and three-zone models lies mainly in the plastic hardening zone,where the stress state is the same as that in the elastic zone.Considering the effect of rock rheology,strain and displacement will increase with time,which will eventually affect the stress,strain and displacement distribution of the surrounding rock of the roadway.By comparing and analyzing the unified solutions of double shear（four zones）,triple shear（four zones）,peak strength solutions,and publicly published M-C and D-P solutions,the variation laws of radial and tangential stresses in the surrounding rock of the roadway caused by different strength criteria are obtained.The results show that when the radius is the same,the magnitude of the radial stress values is generally in the order of peak strength solution>unified solution of double-shear（or triple-shear）>M-C solution>D-P solution;in the elastic zone,the tangential stress is in the order of peak strength solution<unified solution of double-shear（or triple-shear）<M-C solution<D-P solution;in the plastic zone,the tangential stress is in the order of unified solution of double-shear（or triple-shear）>M-C solution>D-P solution.（3）Analysis of factors affecting the elastic-plastic unified solution of deep buried circular tunnels.As the b/m parameter of the unified strength theory increases,both the plastic zone radius and the inner boundary displacement of the surrounding rock of the tunnel decrease.The influence of rheological properties is reflected by controlling the values of the viscoelastic modulus E_k and the initial cohesive strength c₀,and the results show that the plastic zone radius and inner boundary displacement of the surrounding rock of the tunnel decrease linearly with the increase of E_k and c₀.The effect of the internal friction angleφon the plastic zone radius and inner boundary displacement of the surrounding rock of the tunnel is the same as that of rheological properties.The expansion coefficient of the plastic softening zone is determined by the internal friction angleφ,and as the expansion coefficient of the plastic softening zoneηs and the expansion coefficient of the flow zoneηf increase,the plastic zone radius and inner boundary displacement of the surrounding rock of the tunnel gradually decrease.The initial ground stress P0 has a significant influence on the plastic zone radius and inner boundary displacement of the surrounding rock of the tunnel.As P0increases,the plastic zone radius and inner boundary displacement of the surrounding rock of the tunnel increase significantly.（4）A numerical simulation was performed using the power law material model available in FLAC 3D to simulate the creep behavior of rock.The model was fixed at the four sides and bottom,and a lateral pressure coefficient ofλ=1 was selected.The weight of the overlying rock was simplified and applied as a surface load on the model.The stress and displacement fields,as well as the distribution of the plastic zone in the circular tunnel,were simulated.The following conclusions were obtained:Radial stress gradually increases along the radius of the tunnel,while tangential stress first increases and then decreases.The maximum displacement occurs at the inner boundary of the tunnel,which is consistent with the analytical calculation results.The distribution of the plastic zone follows the rule that the plastic zone of the four-zone model is significantly larger than that of the three-zone model.Figure[34]table[2]reference[70]...