Shaking table test on seismic characteristics of trench slope of immersed tunnel

In order to investigate the seismic characteristics of trench slope of immersed tunnel, large-scale shaking table tests were designed and conducted on immersed tunnel trench slope model with the geometric scale of 1:60 on basis of the under-construction immersed tunnel engineering of the Hong Kong-Zhuhai-Macao Bridge, and the seismic characteristics of test model were analyzed. Details of experimental setup were first presented with particular focuses on design of the similitude relation and the model soil. Based on Buckingham-π theory, governing equation of similitude relation was deduced using dimensional analysis, and other similitude relations of physical parameters needed in this test were obtained on basis of the governing equation. Model soil was prepared using a certain amount of sawdust and sand, and a series of laboratory dynamic tri-axial tests was carried out to investigate model soil and field soil. The model soil matching with field soil in terms of seismic characteristics was found. Rigid model box was designed and manufactured with length of 4.5 m, width of 4 m and height of 1.2 m. The differences of seismic response of gradient-changing slops under seismic waves with different spectra, peak accelerations and frequency similitude ratios were investigated through shaking table tests and dynamic response of the gradient-changing slope was discussed. Boundary effect of model box was verified, and acceleration response at boundary was close to that at center, which was further compared with other test results. The results show that soil shows significant amplification impact on the input seismic wave. Acceleration response of the slop surface shows obvious difference excited by different sorts of seismic waves, but the amplification factor distribution trends of peak ground acceleration (P_GA) are nearly the same in test cases of different peak acceleration inputs. The amplification factor of P_GA for gradient-changing slops increases with the increase of the frequency similitude ratio under seismic wave with different frequencies.