Analysis On The Stress Mechanism Of Tunnel Anchors Of Large-scale Suspension Bridges In Urban Ecological Areas And Their Interaction With Tunnels

Compared with the gravity anchorage,the tunnel anchorage has the characteristics of less disturbance to the surrounding rock,so it is often preferred when the surrounding rock quality is good,but the failure mode of the anchoring system are different under different geological conditions,it is necessary to study the specific engineering failure mode on the basis of summarizing the existing failure mode.In this paper,the tunnel anchor of Qingshan Lake suspension bridge in Hangzhou and its adjacent tunnels are taken as the research object,numerical calculation method is adopted to study the failure mode of anchorage system,optimization and sensitivity analysis of design parameters of anchor plug body,and methods to reduce the interaction between tunnel anchor and adjacent tunnel construction.The main results are as follows:(1)Based on the Mohr-Coulomb model and the elastic-brittle-plastic damage constitutive model for rock mass,the stress characteristics of the anchoring system in the three-dimensional geological model and the failure mode of the surrounding rock in the generalized model are calculated respectively.The overloading method is used to calculate the bearing safety factor of the anchor plug body,and the failure law of the surrounding rock from the operating load to the ultimate load is obtained.(2)Based on the generalized model,the single factor of the anchor plug body is studied.The results show that the expansion angle and the axial length are positively related to the bearing capacity of the anchor plug body.However,considering the bearing performance and economy,it is more reasonable to control the two factors within a certain range;according to the different bearing effects,the angle between the joint surface and the axial direction of the anchor plug body is named as different bearing models according to the interval,and the “large angle model” has the best bearing effect.The order of sensitivity of the above influencing parameters is: expansion angle>axial length>angle with the joint surface.(3)The interaction between tunnel anchor and tunnel during step excavation is simulated in the real three-dimensional geological model,and the sequence of excavated structure,the orientation of the leading hole and the staggered distance of the face are discussed respectively,providing an optimal construction scheme for the supporting project.