Study On The Bearing Capacity And The Long-term Stability Of Tunnel Anchorage Of Suspension Bridge

Anchorage is a significant part of suspension bridge carried load.There is a great influence on the bridge normal operation by its bearing capacity and long-term stability.As a kind of anchor which takes full advantage of the strength of rock itself,tunnel anchor is gradually cutting a striking figure with the advantages of small anchor volume and little environmental impact.Taking anchorage on the south bank of Fuma Bridge as engineering background,this paper studies the bearing capacity and long-term stability of tunnel anchorage,using the method of theory analysis and numerical simulation.And relevant proposal is given to the volume of tunnel anchorage.The main conclusions in this paper are as follows:On the basis of existing yielding models and creep models of rock mass,in consideration of characteristics of surrounding rock,this paper identified the constitutive models and parameters under instant load and long-term load.In the numerical simulation,the Mohr-Coulomb yield criterion and the CVISC creep model in FLAC3 D are adoptedThis paper performed a 3d numerical imitation about excavation stage of the anchorage.The numerical analysis results has been contrasted with the monitoring data get from construction site.The analysis results indicate that there's uplifted trend of the integral wall rock,and the disturbance of that is less.When the excavation is completed,the three displacements are stable in 5mm and the tensile stress is stable in 0.1MPa.The monitoring data validates the reliability of the analysis results.Numerical calculations about the tunnel anchorage under 1-19 times of designing load have been conducted,to get the corresponding displacements,stresses and plastic zones.The calculation results show that,under the design load,the tunnel anchor and surrounding rock are in the elastic state,the stress condition is good.Under 3-19 times of designing load,the model shows the gradual failure process of the anchor.And the tunnel anchorage approximately can bear 9 times of the designing load as its load-carrying limit,7 times as its right working limit.Creep calculations on the scale of 7 times of designing load have been conducted by FLAC3 D,to analyze the degree of creeping effect under different loads.It is showed that the long-term stability of the anchorage is nice,but the creep displacement accounted for a higher proportion of the displacement of surrounding rock.Under 3-7 times of designing load,wall rock are in steady creep stage,the plastic zone of the surrounding rock has been expanded.Under 7 times of designing load,plastic zone is connected in the back of rock wall.Therefore,the most suitable right working load taking account of rock mass' s creeping effect is about 3 times of designing load.