Shaking Table Tests On Liquefiable Site-Immersed Tunnel

With the development of modern technology and traffic demand,immersed tunnels have gradually become one of the important choices of crossing river and ocean.However,the immersed tunnels are mostly in a complicated marine environment and are shallowly buried in weak stratum.Once the immersed tunnel is damaged during earthquake,it will be difficult to repair or even lead to serious consequences.Thus,it is very important to carry out research on the seismic response of immersed tunnels.In this paper,with the subsea immersed tunnel of the Hong Kong-Zhuhai-Macao Bridge as the background,two types of immersed tunnel models,immersed tunnel with rigid joints and immersed tunnel with flexible joints,are designed and fabricated.The seismic response characteristics of the model soil and immersed tunnel,under different seismic oscillation characteristic input ground motions,different joint stiffness and different site conditions,are discussed through a series of shaking table tests of soil-tunnel interaction system.The main research work and results of this article are as follows:1.Based on the summarization of model boxes for domestic and overseas shaking table tests,the research group independently develops a laminar shear container with alterable stiffness,and an eigenvalue analysis of a 3D finite element model in ABAQUS is carried out.A series of free-field shaking table tests are performed to study the performance of the model container.Test results are discussed in terms of the difference in acceleration time histories and the corresponding response spectra measured at different heights and different horizontal distances from the container wall,the 2-norm deviation method and the spectral ratio method are also used to quantify and evaluate the boundary effect of the shear container.Results shows that the laminar container properly simulate the boundary condition of the actual site.2.Based on the Bockingham ? theory and dimensional analysis method,comprehensively consider the size,bearing capacity of the shaking table and the laminar shear container and other parameters,the scheme design of the shaking table tests of soil-tunnel interaction system was carried out.It mainly includes the determination of the tunnel model size,the design of test similarity rules,the manufacturing of the model soil and immersed tunnel model,the selection of the input ground motion,the loading scheme and the sensors layout.3.Two types of 1/30-scaled immersed tunnel models,immersed tunnel with rigid joints and immersed tunnel with flexible joints,are designed and fabricated,and two sets of the shaking table tests of soil-tunnel interaction system under different joint stiffness conditions are performed.It mainly analyzes the acceleration time histories,response spectra of the model soil and the tunnel structure,the excess pore water pressure ratio of the model soil and strain of the tunnel structure in the two sets of shaking table tests,and summarizes the seismic response rules of the coupled system of soil-tunnel structure under different joint stiffness conditions.4.Two types of site soil,homogeneous site and heterogeneous site,are prepared,and two sets of the shaking table tests of soil-tunnel interaction system under homogeneous site and heterogeneous site conditions are performed.It mainly analyzes the acceleration time histories,response spectra of the model soil and the tunnel structure and strain of the tunnel structure in the two sets of shaking table tests,and summarizes the seismic response rules of the coupled system of soil-tunnel structure under different site conditions.