| With the construction of double steel shell concrete immersed tube tunnel-Shen ZhenZhong Shan Bridge for the first time in China,the attention to immersed tube tunnel at home and abroad is increasing.Since the immersed tube tunnel can be prefabricated in advance and transported directly to the designated location for sinking,the construction efficiency is greatly improved.Compared with the reinforced concrete immersed tube tunnel,the double-steel shell concrete immersed tube tunnel has many advantages,such as high bearing capacity,large stiffness and good ductility,etc.,which gradually show its influence in many domestic projects.However,as the immersed tube tunnel is laid on the seabed,under the action of seismic load,the seismic design of pipe joint is very important.At present,there are many researches on the overall seismic performance of immersed tube tunnel at home and abroad,but few researches on the joint seismic performance of immersed tube tunnel.However,more attention should be paid to the joint as the weak part of immersed tube tunnel.Therefore,it is of great practical value to study the seismic performance of the joint of immersed tube tunnel with double steel shell concrete.In Shen Zhen-Zhong Shan Bridge’s immersed tube tunnel project as the engineering background,immersed tube tunnel at home and abroad was analyzed through reading literature,shield tunnel and other underground structure seismic related research present situation,summarizes the BART method,the dynamic finite element method(fem),the response displacement method,spring-particle-beam model and simplified model of equivalent stiffness five kinds of the common method to seismic analysis.The response displacement method is used to study the seismic behavior of immersed tube tunnel,the dynamic response characteristics of tunnel joints under seismic action are studied by using the dynamic finite element method,and the static finite element method is used to solve the foundation stiffness and then the seismic analysis of tunnel structure is carried out.GINA check hose model is established by using ABAQUS finite element software,the GINA sealing of the simulated research,found that GINA water-stop coping with the existence of the tip,the stress distribution of contact area at the top and side steel shell difference is bigger,the top of the contact stress is greater than at the bottom of the contact stress,relative to the end of the steel shell at the bottom of the contact area is large and smooth,with better sealing at the top so GINA waterproof of the weak link is at the bottom,under the condition of normal compression,leakage will occur in the check at the bottom of the hose.The mechanical model of pipe joint is established,and the values of axial stiffness,tangential stiffness and torsional stiffness of spring are analyzed.Based on the static finite element method,the spring stiffness of the vertical,horizontal and longitudinal foundations of the immersed tube tunnel are calculated.Using Midas Soil Works software for free field of soil around the tunnel pipe joint analysis of soil layer model is established,on the one dimensional response analysis of soil,changing with depth,the time history curve of the acceleration response of each soil layer,speed of response time history curve,and displacement response time history curve of the equivalent shear modulus of the soil,the equivalent damping ratio,etc.The 8-node linear 3D solid unit C3D8 R in ABAQUS was used to establish the pipe section calculation model of immersed tube tunnel.In terms of material constitutive model selection,the elastic model was adopted for the concrete inside the pipe section.The horizontal concrete shear bond adopts the concrete damage plastic model.The steel sections Q235 and Q345 were defined as classical metal elastoplastic materials by steel structure hyperbola model.Rubber materials such as GINA stopper are mooney-Rivilin model.Using dynamic time history method of immersed tube tunnel socket joint seismic characteristics are studied,by entering the x,y,z to El Centro earthquake wave,institute of socket joint section seven key points and get their stress-time history curve,displacement time history curve and the relative displacement of roof and floor-time history curve,found under seismic load,the first immersed tube tunnel side frame structure may be in tension serious side compression,this state of structure is very easy to cause adverse structural failure damage,should strengthen the strength of the joint of side wall and the wall,The stiffness of the vertical steel shear bond and the friction force of the two pipe joints meshing with each other can be considered.Secondly,the joints between the side wall and the roof and between the middle wall and the middle partition have very large changes of compressive and tensile stress,which is the weak position in the anti-seismic of immersed tube tunnel.In the design of immersed tube joint,attention should be paid to the joints at these several pipe joints,and corresponding strengthening should be carried out.Finally,in the y direction input seismic wave,the lateral displacement of the wall should be greater than the displacement of the central,basic from the central tunnel on both sides to gradually decreases,and the tension deformation are prone to damage,stele easily happened first in the earthquake damage,this kind of circumstance should be combined with the actual project need not pursue too wide or too large pipe cross section,reduce the distance of the side wall to wall.The results show that the maximum joint opening is less than the joint opening caused by the seismic action considered in the design,which indicates that the existing joint layout of the pipe joint can effectively meet the seismic requirements. |
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