Scattering Of P And SV Waves By Group Cavities In A Layered Half-space

According with the appearance of more and more underground buildings, people pay more attention to the seismic response of the site. The analysis of wave propagation in layered soil is important both in theory and engineering. J.P.Wolf derived dynamic-stiffness matrix of elastic layered soil, as well as green's functions for distributed loads acting on inclined line in a layered site, which formed a complete theory for wave propagation in layered site and dynamic soil-structure interaction. How to extend Wolf's theory to the case of P and SV waves will be mainly resolved in this paper.Amplification of P and SV waves by group cavities in a layered half-space is analyzed by indirect boundary-element method in frequency domain. The free-field response was calculated to determine the stress on the line which will form the surface of the cavity. Then fictitious distributed loads are applied on the same line in the free field to calculate Green's functions for the displacements and stress, and the displacements response arising from the waves in the free-field and from the fictitious distributed loads are summed up to obtain the solution.The amplification of P and SV waves by group cavities in a single layered resting on a half-space are studied by using the indirect boundary-element method. Then the difference of amplification by group cavities or a cavity is compared. And analyze the impact of the incidence angle, incident wave frequency, stiffness ratio and the distance of the cavities according to the results. The results indicate that with the increase of the incident wave frequency, the amplitude distribution become complex gradually; with the increase of the stiffness ratio, the amplitude increased in general, the more the incident wave frequency close to the resonance frequency, the evident the trend is; the closer two cavities are, the more they interact with each other, then the more amplification that the earthquake waves act on the site. This method can be used in the dynamic analysis of underground structure such as cavity.