Study On Interaction Mechanism And Application Of Tunnel Surrounding Rock And Supporting Structure

The interaction between the surrounding rock and the supporting structure is the core issue of the tunnel construction,which directly affects the size of surrounding rock pressure,the type of supporting,the selection of supporting parameters,and the determination of the timing and supporting stiffness.It is of great significance and application value to carry out relevant research for tunnel design and tunnel stability evaluation.Based on the Shiaoding tunnel,this paper systematically studies the interaction between tunnel surrounding rock and supporting structure through theoretical analysis,on-site monitoring and numerical simulation,and obtains the following main research results:(1)Aiming at the shortcomings of the existing codes in calculating the surrounding rock pressure of shallow buried bias neighborhood tunnel,the theoretical calculation formula of surrounding rock pressure of shallow buried bias neighborhood tunnel considering the interaction of the successive construction of left and right tunnels is deduced.(2)A quantitative evaluation method for the stability of surrounding rock and supporting structure was established.Based on the example of the Shiaoding tunnel project,the curves of the interaction between the surrounding rock and the supporting structure under different supporting timings and different supporting stiffnesses are established respectively.By determining the coordinates of equilibrium points in the diagram,the safety factors of surrounding rock and supporting structure of the tunnel are calculated.(3)According to the on-site monitoring data of deformation,surrounding rock pressure,steel arch stress and shotcrete stress of typical section surrounding rock and supporting structure of Shiaoding tunnel,the safety factor of surrounding rock and supporting structure is obtained,and combined with on-site monitoring data of surrounding rock pressure,the rationality of theoretical calculation formula of surrounding rock pressure of shallow buried bias neighborhood tunnel considering construction influence is verified.(4)According to the theoretical calculation formula of tunnel surrounding rock pressure with shallow buried bias neighborhood tunnel,the influence of factors such as tunnel ground slope angle,tunnel net distance and buried depth on the distribution law of tunnel surrounding rock pressure is analyzed.It is found that the lateral pressure coefficient on the inner side of the left and right tunnels of the neighborhood tunnel is related to the slope angle of the ground,the clearance of the tunnel and the depth of the tunnel,while the lateral pressure coefficient on the outer side is only related to the slope angle of the ground.The first tunnel is affected by multiple excavation disturbances.The force acting on the first tunnel is greater than that on the second tunnel,and the bias phenomenon is more serious.According to the theoretical calculation formula deduced in this paper,the calculation is more in line with the reality and can obtain more safe and reasonable supporting structure design parameters,and the results have certain guiding significance for the design of similar projects.(5)The deformation law of surrounding rock,stress of surrounding rock,distribution of plastic zone and stress of supporting structure under different excavation methods are studied by numerical simulation.The deformation of surrounding rock,stress of surrounding rock,distribution of plastic zone and stress of supporting structure are all better when excavating with CD method than when excavating with reserved core soil method,and recommended that excavating with CD method be used in the construction of grade V surrounding rock.