Simulation And Applied Research Of Multi Body And Multi Domain Elastic Wave Scattering Based On Fast Boundary Element Method

In recent years,frequent earthquakes have caused great damage to people's personal and property safety,and how to reduce the damage caused by earthquake disaster has become the focus of attention.However,as one of the three factors that affect the ground motion,the local site has a significant impact on the seismic response in the near surface.In real life,people to build the underground tunnel,subway station,pile foundation,mining wells and all kinds of underground pipelines,natural lava formation,or cave disasters in the mountain cracks,underground fault will affect the propagation of seismic wave,or the earthquake amplification or reduction,but different local site types will be different reaction.The existing regulations at home and abroad only point out that the buildings,structures and so on should be avoided as far as possible the qualitative requirements of the uneven site,but did not make specific provisions.Aiming at the above problems,based on the traditional boundary element method,the introduction of the fast multipole algorithm is studied for multi domain elastic wave scattering problems,in order to realize the quantitative analysis of non-uniform ground motion.First,a large number of multi domain and multi domain elastic wave scattering in solid is simulated,and the accuracy and efficiency of the developed method are verified.Secondly,the numerical results show that the displacement amplification effect on the surface of the half space is more significant than that of the two-dimensional SH wave.Especially in the low frequency region,the displacement amplitude reaches 5.Under the condition of high frequency SH wave incident,the cavity group and the soft inclusion group have obvious barrier effect,and the displacement amplification and the reduction area of the surface of the top half of the hard inclusion group will appear alternately.The scattering of P wave and SV wave in the whole space is different from that of the single inclusion,and the spatial distribution of the total wave field is more complicated.Under the plane P wave incident,the scattering effect of the inclusion body on the elastic wave is more significant with the increase of the incident wave frequency.For ka=1.0,the wave velocity ratio is 1/3 of the inclusion internal and external,Due to the coherent effect of the multiple scattering of the inclusion body,the inclusion body shows that the displacement amplitude is up to 2.2.Finally,on the basis of the verification of the accuracy and efficiency of the two scattering problem of the elastic wave with a crack,the influence of the crack group on the displacement of the mountain surface is analyzed.The presence of a small number of large size cracks in the plane P waves is always a barrier to the vertical displacement of the mountain surface.However,the maximum vertical displacement amplitude of the mountain surface with a large number of small cracks increases by about 9.7% compared with that without cracks,which shows that the existence of the crack group has a great influence on the vertical displacement of the mountain.In addition,it is worth noting that the maximum horizontal displacement of the surface of the mountain is always the phenomenon of amplification.In summary,this paper aiming at large-scale multi-body multi domain and the crack elastic wave scattering developed fast multipole boundary element method for indirect corresponding problems,provides a theoretical basis for the quantitative analysis of complex ground motion.