Derivation Of Reflection And Transmission Coefficients Of Seismic Waves In Viscoelastic Media

Seismic wave is appeared when the reflection and transmission waves, which aregenerated by a stress wave after it reaches an interface, superimpose with each other.It is a disturbance transformed from a stress wave. It propagates through rock and soilmedia and loses its energy gradually. The wave ray is not a straight line, but the curvewith complicated forms after a bunch of reflections and transmissions. When seismicwave incidents vertically into varieties of interfaces, many times of reflections,transmissions and diffractions are generated; when obliquely, it will also generatewave pattern transformation between P-wave and S-wave. In this thesis, the wavepattern transformation between P-wave and S-wave is considered, the attenuation lawof seismic wave is researched.The main work is summarized as follows:(1) In this thesis, the researches of previous in the theory and practicalapplication of acoustic and seismic wave attenuation Analysis and summary, lays atheoretical foundation for in-depth study of this thesis.(2)Through the formula derivation of reflection and transmission c oefficients ofseismic wave in viscoelastic media, the propagation laws of seismic wave inviscoelastic media and the reflection and transmission coefficients of longitudinal andtransversal wave in three-dimensional viscoelastic media are achieved.Simultaneously, the reflection and transmission coefficients of elastic medium withviscoelastic medium is compared and analyzed. It lays also a foundation for furtherresearches of energy decay of seismic wave.(3) This thesis is based on the theoretical formula of reflection, transmissioncoefficient of seismic wave in the double-layer media, the formula of seismic waveenergy retention ratio in a two layer media is further derived in this thesis, and theattenuation law with the change of angle of incidence is analyzed. And the law withthe change of energy attenuation ratio is analyzed.(4)In order to study the theoretical solution of the seismic wave energy retentionratio, this text establishes a two layers of the soil medium model using ADINA finiteelement software,and gets the value of energy retention ratio under Finite elementanalysis, in addition,comparative analysis of the theoretical solution.(5)In order to study the seismic wave energy decay for the actual impact of theproject, and in order to further verify seismic wave energy retention ratio of the theoretical formula. A soil-foundation-frame construction model is established basedon the established medium model in two layers of soil in this thesis. When seismicwave is incidental at the bottom of the foundation, the interlayer displacements andinternal forces of the framework of the upper structure were compared before andafter the attenuation of energy retention ratio.At the same time, the interlayerdisplacements and internal forces of the framework of the upper structure werecompared for seismic wave is direct incidental from the soil and the seismic waves areincidental from the bottom of the foundation after attenuated according to energyretention ratio.