Study On Seismic Dynamic Response Characteristic And Shock Absorption Measures Of Highway Bridge And Tunnel Lap Structure

In order to deal with the complex terrain with steep slopes,high mountains and deep valleys,the abutment is usually set in the tunnel when building expressway,also called bridge and tunnel lap structure.Under the strong earthquake,the bridge and tunnel lap structure constructed in soft rock overlapping areas is extremely easy to damage or destruction,and will interrupt the traffic,resulting in huge economic losses.Therefore,under the action of earthquake,the dynamic response characteristics and failure mechanism of the bridge and tunnel joint structure need to be solved urgently.The study of the seismic dynamic response and the damping measures of the bridge and tunnel overlapping structure has become a hot issue in the geotechnical engineering.Based on the National Natural Science Foundation Project of China "Research on Seismic Dynamic Response of Bridge and Tunnel Lap Structure Based on Damage Accumulation Effect"(No.:51408617),and taking the bridge and tunnel of Ma pun tunnel and Ma Bu Chong bridge as the background,the shaking table test of the expressway bridge and tunnel joint structure was carried out.What's more,the numerical simulation of bridge and tunnel overlapped structures was carried out by using finite element software.In addition,on the basis of the mutual validation of the shaking table test results and the numerical simulation results,the internal force analysis,the damping measures and the effect analysis were carried out on the bridge and tunnel joint structures under different conditions.The work and main achievements of this paper were as follows:(1)Based on the similarity theory,the shaking table test of bridge and tunnel overlapped structure with a geometric ratio of 1:50 was designed and completed.According to the test requirements,the similarity constants of physical quantities,the mix proportion of similar materials and physical and mechanical parameters were determined.This paper introduced the boundary of model box processing,bridge and tunnel joint structure production process,measuring point arrangement and seismic wave loading scheme.(2)According to the data collected by the shaking table test,the changes of the dynamic strain,dynamic displacement,dynamic earth pressure and acceleration of the bridge and tunnel joint structure were studied under the action of the different loading direction of Wenchuan wave and the different acceleration peak of El Centro wave.Major results include that in most cases,the inverted arch is mainly subjected to tensile stress,the arch foot and the vault are mainly subjected to compressive stress,and the pile foundation bears the cyclic loading of tension and pressure.The seismic wave along the axis of the tunnel plays a leading role in the dynamic displacement of the bridge and tunnel lap structure,and the dynamic displacement of each measuring point increases with the increase of the peak of the seismic wave excitation peak.The acceleration amplification factor of the tunnel vault and the inverted arch subsides from the hole along the tunnel axis,yet the acceleration amplification factor of the bridge deck from the span of the bridge to the tunnel entrance.The acceleration of the observation section from the inverted arch to the vault increases on the standard section.(3)The finite element software Midas GTS/NX was used to establish the three-dimensional numerical model of the bridge and tunnel overlapping structure.By applying the El Centro wave with different exciting strength,and on the basis of numerical simulation and model test mutual verification,a large number of numerical simulation work was been carried out.The results showed that the change trend of the two results is basically the same.On the basis of mutual validation between numerical simulation and model test,a lot of numerical simulations were been carried out.The internal force distribution of standard segment lining under different excitation intensity was analyzed.Taking the excitation peak value of 0.4g as an example,by installing a 20cm thick damping layer on the lining of the standard section and the enlarged section,the dynamic response characteristics and changing rules of bridge and tunnel overlapped structures with or without damping layer were studied.