Isolation Performance Of T-shaped Partially-embedded Periodic/gradient Surface Wave Barrier

ABSTRACT:The band gap characteristics of periodic structure mean that waves in the band gap cannot propagate through the periodic structure.So it is of great practical significance to apply periodic structure to seismic wave isolation.Based on the periodic structure theory,T-shaped partially embedded periodic/gradient surface wave barriers were designed.The band gap characteristics and transmission characteristics of the wave barrier were simulated by the finite element software,COMSOL MULTIPHYSIC 5.2,and the site isolation experiment was carried out.The effects of different embedding depths,number of periods,whether the barrier is defective,and depth of gradient distribution on the isolation performance were considered.The experimental and numerical results were compared and analyzed.At the same time,in order to achieve effective isolation in the low frequency region,the effects of embedding depth,physical parameters and geometric parameters on the band gap were further discussed.Namely,isolation performance curves of three kinds of gradient wave barriers,the embedded depth of barrier,the size of upper structure or the height of lower structure in gradient are calculated.And the isolation effect of the periodic/gradient wave barrier designed on the EI-Centro seismic surface wave was given.The following conclusions were obtained:1.The experimental results show that the T-shaped partially embedded periodic surface wave barrier can effectively attenuate the surface wave and the attenuation amplitude increases with the increase of the number of periods.The variation of the embedded depth can effectively adjust the frequency range of the attenuation domain.If the embedded depth increases,the center frequency of the attenuation domain increases.When the barrier is defective,the barrier's ability to protect the defect location becomes weak or disappears.The barrier still has better isolation effect away from the defect location.A gradient wave barrier with a linear variation in depth has a wider attenuation domain than the periodic wave barrier.2.Numerical simulation results show that the depth of the periodic wave barrier embedded in the soil has a significant impact on the performance of isolation.The smaller the embedded depth,the better the band gap characteristics of the barrier in the low frequency range.Adjusting the material parameters and geometric parameters can also effectively adjust the band gap characteristics of the barrier.The greater the difference of material parameters between the barrier and soil,the better the effective isolation of low frequency surface waves.An increase in the size of upper structure increases the bandwidth while reducing the center frequency of the bandgap.Compared with the periodic wave barrier,the three gradient wave barriers significantly widen the frequency range of the attenuation domain and improve the isolation performance of the barrier.3.The comparison between the experimental results and the numerical results shows that when the parameters,such as the embedded depth,the number of periods,the defect form and the gradient of the embedded depth are changed,the experimental results have the same variation with the numerical results and have similar frequency ranges of the attenuation domain.4.The T-shaped partially buried periodic/gradient surface wave barrier has good isolation effect on the surface wave of EI-Centro earthquake.