Research On The Performance Of T-shaped Barrier For Surface Wave In Transversely Isotropic Soil

Earthquake disasters can cause serious losses to human beings.Finding effective seismic isolation methods to protect the structures has become an important research topic in the field of civil engineering.As we all know,the skeleton of natural soil is generally anisotropic.Aiming at the problem of seismic isolation in transversely isotropic soil,this paper proposes a partially embedded T-shaped barrier for surface wave based on the elastic wave band gap（BG）characteristics of periodic structures.Using the finite element method combined with the Bloch-Flquent theory,a dimensionless analysis of wave governing equations and corresponding boundary conditions is carried out,and the dimensionless material parameters that determine the BG characteristics are deduced.The influence of material parameters and structural parameters on the BG properties of wave barriers is studied,The stability of the T-shaped surface wave barrier under seismic waves is analyzed.With the goal of broadening the wave barrier’s attenuation range and optimizing the isolation performance,combined wave barriers and gradient wave barriers are proposed and the frequency response function is calculated.The seismic isolation effect of the T-shaped surface wave barrier on the El Centro waves is verified.The conclusions are as follows:1.The density ratio of the barrier to the soilρ^b/ρ^s,the shear modulus ratio G^b/G_h^s,the vertical to horizontal shear modulus ratio of the soil G _v^s/G_h^s,and the Poisson’s ratioμ^b,μ_v^s _h,μ_h^s _vandμ^s_hh are seven independent dimensionless material parameters that directly affect the BG characteristics of the wave barrier in the transversely isotropic soil.Among them,the the first three parameters have greater impacts on the band gap characteristics,and the Poisson’s ratio has little.2.The soil shear modulus ratio G _v^s/G_h^s is an important parameter that causes the change of the band gap characteristics of the barrier.The band gap width in a completely isotropic soil is much smaller than that in an anisotropic soil.It is difficult to accurately describe the band gap characteristics of the wave barrier in the actual site if the soil is assumed to be completely isotropic.3.The study of dimensionless material parameters can be used to guide the selection of wave barrier materials in actual sites.When designing a wave barrier in a site with a high and very high degree of soil anisotropy（0.5v^s/G_h^s≤0.9）,the shear modulus ratio G ^b/G_h^s does not need to be too large,and a wider BG can be obtained by increasing the material density ratioρ^b/ρ^s.In a site with a very low degree of anisotropy（0.9v^s/G_h^s≤1）,increasing the material shear modulus ratio G ^b/G_h^s can effectively expand the BG,but if the material density ratioρ^b/ρ^s is too large,it will be difficult to generate the BG.4.When the length of the lower round rod is constant,different seismic isolation requirements can be met by adjusting the exposure-to-buried ratio.When the soil anisotropy is high and very high,increasing the exposure-to-buried ratio can expand the BG;when the soil anisotropy is very low,the exposure-to-buried ratio should not be too large.5.Compared with periodic wave barrier,single-parameter gradient wave barrier of typeⅠcan attenuate surface waves in low-frequency regions,and two-parameter gradient wave barrier of type II can effectively expand the BG.Both of them can save material consumption and produce good seismic isolation effects,and have important practical application value.6.Partially embedded T-shaped periodic barrier for surface wave and two-parameter gradient wave barrier of type II have good seismic isolation effects for El Centro seismic waves.In the main frequency range of seismic waves,the acceleration amplitude is significantly attenuated,and the attenuation amplitude exceeds 90%.