Seismic Isolation Effect of Seismic Metamaterials Based on Fast Multipolar Indirect Boundary Element Method

China is one of the countries in the world that have suffered more severely from earthquake disasters. In recent years, catastrophic earthquakes have greatly harmed people's lives and properties. The seismic isolation design of major engineering structures to carry out seismic isolation design has become an indispensable part of the structural design. The Fast Multipole Indirect Boundary Element Method (FMIBEM) was applied to the simulation of seismic wave scattering by 2D seismic metamaterials, and the seismic Isolation effect of a kind of periodic seismic isolation material, i.e., the geotechnical composite seismic metamaterial (RSCSM), was solved. Based on the accuracy verification, the bandgap structure of RSCSM and the seismic isolation effect and bandgap range under different single-cell structures were numerically analyzed in detail. The results show that the broadband scattering of seismic waves by large seismic metamaterials can be effectively dealt with by using FMIBEM; RSCSM can isolate the ultra-low-frequency bandgap of seismic waves, and the width of the bandgap generated by the square-cell structure (0.5~17.0 Hz and 54.0~72.0 Hz) covers the main frequency bands of seismic wave hazards (0.5~2.0 Hz), with an isolation effect of up to 35% or more; and the effect of changing the single-cell structure of RSCSM can be analyzed. Single-cell structure of RSCSM has an important effect on the seismic metamaterial bandgap structure. The bandgap generated by the square cell structure is approximately 0.5~17.0 Hz and 54.0~72.0 Hz; the bandgap generated by the rhombic cell structure is approximately 0.5~20.0 Hz; the bandgap generated by the rhombic single-dot cell structure is approximately 0.5~16.0 Hz and 40.0~57.0 Hz; and the bandgap generated by the rhombic double-dot cell structure is approximately 0.5~14.0 Hz. The filling rate of the hard scatterer also has an important impact on the bandgap, which can be significantly influenced by the same filling rate. The tetragonal cell produces a wider bandgap at the same filling rate, and the tetragonal cell produces a better bandgap effect at lower filling rates. The rhombic single-dot and rhombic double-dot cell structures can only produce better bandgap effects at very high filling rates. This study provides an efficient method for the simulation of seismic wave scattering by the seismic metamaterials, and the conclusions of the study can provide a partial scientific basis for the design of foundation seismic isolation. © 2024 Sichuan University. All rights reserved.