Research of Shaking Table Model Tests on Immersed Tunnels under Different Conditions

To study the seismic response and anti-seismic behaviour of immersed tunnels at different sites, shaking table tests were conducted in three sets. The reduced-scale ratio of the tests was 1:30. The site conditions adopted in the tests were dry sand, saturated sand, and saturated sand under an overlying water layer. The experimental results show that when the peak ground acceleration (PGA) of the input excitation is 0.1g, the acceleration amplification factors of dry sand, saturated sand, and saturated sand under an overlying water layer exhibit a magnifying trend. No soil liquefaction occurred in the saturated sand sites. When the input PGAs are 0.2g and 0.4g, the acceleration of the soil deposits of the dry sand site continues to increase, whereas the acceleration of the surface points in the saturated sand sites decreases owing to sand liquefaction. When the input PGA is 0.4g, the maximum reduced acceleration percentages of the middle tunnel elements in the three sets of tests are11.1%, 7.6%, and 9.4%, respectively, compared with those of the end tunnel elements. The flexible joints have a shock absorption effect during the shaking process. The development trends of pore water pressure of the soil deposits correlate well for the saturated sand and saturated sand under an overlying water layer. In addition, the results of the three sets of tests indicate that the nodes between the middle wall and the base slab are the weak positions of the tunnel model.