Research On Elastic Analysis And Time-varying Effect Of Rock Mass-Rock Bolts Coupling System Of Circular Tunnel Based On Point Load

For geotechnical engineering,currently there are gradually increasing cases of tunnel construction and underground engineering,but during the construction process,there will always be surrounding rock deformation and tunnel cracking.The deformation of the surrounding rock continues to increase,causing the tunnel to lose stability and collapse Disasters such as disasters will also occur,which will have a greater impact on the effectiveness and safety performance of the supporting structure.In order to improve the stability of tunnels and underground engineering,anchors are often used for reinforcement,but the long-term interaction mechanism of surrounding rocks and anchor supporting structures under time-varying effects is not well known.Therefore,how to reasonably consider the rheological behavior of surrounding rocks and explore the coordinated deformation mechanism and long-term dynamic relationship between surrounding rocks and support becomes an urgent problem.In the construction of tunnels and underground engineering,laying a theoretical foundation for evaluating the safety of anchoring engineering and optimizing the support design has important theoretical significance and application value.In this paper,when exploring the coupling rheology of surrounding rock-anchor supporting structures,based on the "point load model" of the circular tunnel anchoring engineering mechanics research model,the surrounding rock and the anchor are regarded as independent rheological bodies.And assuming that when the anchor rod and surrounding rock are both viscoelastic materials,the long-term change mechanism and mechanical laws of the tunnel support project with a circular cross section are comprehensively analyzed in detail using theoretical analysis,mechanical calculations and numerical simulations.The analysis research has mainly completed the following:(1)Based on the load transfer mechanism,the basic mechanical model of the "point load"model is selected,and the elastic solution of the coupled rheological model of the surrounding rock-end-anchor anchor support structure is selected using Maple.The law and characteristics of the stress and displacement of the rod and the stress field and displacement field of the surrounding rock over time.The results show that the effect of stress field,displacement field and axial force before and after superposition of the concentrated force acting on the coupled model of surrounding rock and end-anchored anchor under the action of point load is equal.The radial stress tends to the original rock stress as the radial distance increases,the tangential stress decreases as the radial distance increases and then to the original rock stress,and the radial displacement increases as the original rock stress increases,that is,the original rock stress It can promote the radial displacement caused by the stress release phenomenon of the inner wall of the tunnel excavation.Increasing the elastic modulus of the anchor can effectively reduce the displacement of the inner wall of the tunnel and its deep part.(2)Based on the elastic solution of the "point load" model,consider the viscoelastic theory to solve the Laplace space solution.The inverse change of the Laplace space solution is used to obtain the time-varying coupling of the surrounding rock-end-anchored anchor support structure.Effect model rheological solution.The rheological model selects the KM and KK models to quantitatively analyze the influence of different viscous parameters on the support effect and selects different support parameters and material parameters for analysis.The results show that the viscoelastic model used by the anchor and surrounding rock determines The change of the mechanical state and deformation of the anchor and surrounding rock is decisive for the change of the confining pressure of the anchor.The mechanical parameters of different rheological models have an effect on the change of the stress and displacement field with time.The stress field,displacement field and anchor axial force of the surrounding rock show obvious time correlation.The displacement field of the surrounding rock decreases with the strengthening of the supporting effect.The influence of the viscosity coefficient of the surrounding rock on the displacement of the surrounding rock is very obvious.(3)Based on the theoretical model and the secondary development of the finite difference software FLAC3D,the rheological deformation characteristics of the anchor are realized,and the long-term rheological behavior of the circular tunnel under the support of the anchor is numerically analyzed,and the analytical solutions are further compared and analyzed.The degree of agreement with the numerical solution,the difference analysis and comparison of rheological models between different anchor-wall coupling coupling time-varying effect models,the comparative analysis of the analytical solutions of the distributed force model and the point load model,the rationality of the model and the Evaluation of applicability.