| Tunnels have the advantages of shortening the driving distance and improving driving safety,which are widely used in traffic engineering.When the tunnel is completed,the stress concentration and displacement will appear in the boundary of surrounding rock and lining.If the stress concentration and displacement are too large,it will affect the tunnel construction and operation quality,even cause the safety accident.Seismic wave and other dynamic loads also have great influence on the safety of tunnels,so it is very important to study the mechanical behavior of tunnel under static and dynamic loads.The mapping functions of highway tunnels with various cross sections are calculated by iterative method.Based on complex variable function,the problem of stress and excavation displacement after the excavation of horseshoe-shaped road tunnel is studied.The excavation problem of the tunnel without lining is simulated by the finite element software ANSYS.Combined with the horseshoe-shaped tunnel,the distribution of the dynamic stress concentration coefficients under the plane P wave incidence is solved,and the influence of different dimensionless wave numbers on the distribution of the stress concentration coefficients is analyzed in this paper.The results show that the iterative method solves the tunnel mapping function with high precision,strong adaptability,easy programming and fast convergence.Stress concentration is occurred in arch foot of tunnel,and the maximum settlement and uplift of excavation were appeared in arch crown and center of inverted arch respectively.The numerical results of tunnel excavation with no lining are in good agreement with the analytic solution.The existence of the lining can relieve the stress concentration and reduce the deformation of the surrounding rock.As the incidence of P wave,the dynamic stress concentration is occurred near the tunnel,and the dynamic stress concentration factor is larger when the dimensionless wave number of the incident wave is low. |
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