Wave Propagation In Nearly Saturated Half-space Soils

Wave propagation in porous medium is an important subject in geotechnical and earthquake engineering. In virtue of the assumptions that the soil was one-phase elastic media or two-phase fluid-saturated medium, Some Wave propagation in soil was researched by scholars. Soil is a kind of three-phase porous media, otherwise, because of the complexity of coupling action in three-phase soil, few researches on unsaturated or nearly saturated soil are done. Taking soils as three-phase medium, a study on wave propagation in nearly saturated soils is presented in this dissertation.The thesis reviews the previous researches on theory of propagation of body wave and Rayleigh wave in fluid-saturated porous media briefly, and set up a wave motion equations for three-phase nearly saturated soils based on the theory of mixture and Darcy's law. Solutions for those equations are derived, numerical expressions of body wave velocities and attenuations are presented, then the influences of frequency and saturation degree on them are analyzed systemically. By analyzing the dynamic equation of nearly saturated soil, the secular equations of Rayleigh waves in a nearly saturated half-space soil are developed. Rayleigh wave dispersion characteristics and its displacement in a nearly soil are discussed.Numerical results shows that the characters of dispersion curve of elastic waves in nearly saturated soil are similar to those in fully saturated soil but a slight decrease of full saturation may cause a much greater displacement compared with a fully saturated soil. In addition, the saturation's influences on the velocity and attenuation of each elastic wave are indicated in the paper. And the research in this paper establishes the theoretical basis of further study of nearly saturated porous media, the results have a practical significance in body waves and Rayleigy wave's applications in geotechnical engineering and geophysics.