Research On Wave Propagation Characteristics And Dynamic Response In Partially Saturated Soils

The study of wave propagation in soils is one of important branches in soil dynamics field and has been becoming fundamental importance to several disciplines, such as Civil Engineering, Seismology, and Geophysics etc. In this dissertation, a thorough, comprehensive and systematic study on the wave propagation characteristics and dynamic response in partially saturated soil is perfomed on basis of the dynamic control equations of tri-phase porous medium.Firstly, a comprehensive analysis on the property of every phase in partially saturated soils is executed in this dissertation from microstructure view, including soil particles distribution, stiffness, density, damping and saturation, all of which are mostly concerned in soil dynamic research. The dynamic characteristics of air bubble in partially saturated soils are discussed in particular. Moreover, the conformation and distribution properties of air bubble are studied, and the important influence of air compression upon the fluid compressibility and volumetric deformation of partially saturated soils are analyzed, as well as the influence of air bubble vibrating on dynamic characteristics of surrounding fluid and porous medium is presented. Based on the microcosmic dynamic characteristics of partially saturated soils, a simplified model of partially saturated soils is suggested in this paper and its rationality is also evaluated. Dynamic equations of partially saturated soils are deduced detailedly and analyzed systematically. According to consistencies and differences between Biot's theory and mixture theory, the dynamic equation in tri-phase medium is suggested for the study of wave propagation in partially saturated soils. The applicability of the theory for partially saturated soils is discussed and the influence of soil permeability and distribution characteristics of pore size on wave theory is analyzed particularly.Based on wave theory of tri-phase partially saturated soil, the numerical method is employed to study the propagation characteristics of the three body waves (the first P wave, the second P wave and S wave) in partially saturated soils. Considering the relationship between void ratio and the stiffness of soil skeleton, the influence of void ration, saturation degree, frequency and Poisson's ratio etc. upon the propagation and attenuation of every body wave in partially saturated soil is analyzed comprehensively. Conclusions of former test results are used to verify the research results in this paper; the consistencies and differences of wave propagation in partially saturated soils, saturated soils and air saturated soils are also analyzed.According to the wave propagation theory of partially saturated soils, considering the compressibility of soil particles and fluids as well as the viscosity of fluids, the propagation characteristics of Rayleigh wave in partially saturated soils is firstly comprehensively and systematically studied. Taking the influence into consideration that the permeable condition at the boundary, the influence of saturation degree, frequency, permeability and Poisson ration upon the propagation velocity, the distribution of displacement, the energy ratio of every component wave and particle motion is studied using numerical methods. Based on above results, compared with propagation characteristics of Rayleigh wave in saturated soil, this paper shows that Rayleigh wave mainly indicates the characteristics of shear wave and is little affected...