Influence Of Water Level Change On Dynamic Response Under Moving Loads And Vibration Isolation In Saturated Soil

The environmental vibration problems have begun to affect the safety of buildings and the normal life of residents,and have attracted more and more attention in the society.Traffic is one of the main sources of environmental vibration.The vibration of vehicles and trains generally transmits energy to buildings through the soil medium,so it is very important to study the propagation and attenuation of vibration waves in soil.In the existing research,the soil is generally simulated as an isotropic medium that elastic media and saturated media are usually used.Even the study of layered soil mainly focuses on the difference of soil properties.However,soil properties may also change in different seasons and environments,one of which is the groundwater level.Due to the change of groundwater level,the soil may have a dry soil layer and a saturated layer at the same time.So the overlying elastic on saturated soil foundation can simulate the soil more realistically,which is of great significance and value for the research and management of environmental vibration.The research contents of this paper are as follows:1.The saturated half-space dynamic response problem is described based on the Biot porous media equation.Fourier transform and integral are used to solve the general solution of the wave field in the frequency-wavenumber domain,and then the wave field expression in the time domain-spatial domain is obtained by the Dirac function and the Fourier inverse transform.The wave composition in the dynamic response of saturated soil is analyzed in the wave number domain,and there are P2 waves in saturated porous media compared to elastic media.;the influence of different loads and soil parameters on the vibration of the saturated foundation is studied in the spatial domain.Under the action of high-speed and high-frequency loads,the dynamic response of saturated media is quite different from that of elastic media,and the water content in pores and the viscous coupling coefficient will change the media dynamic response.2.The overlying elastic layer on saturated soil half-space is used to study the problem of the dynamic response in the foundation with a groundwater table below the surface.The soil layer above the water level is assumed to be an elastic medium,and the motion of waves in the elastic medium is described by the degenerate form of the Biot porous medium equation.Saturated soils below the water table are simulated using porous saturated media.The transfer matrix between the elastic layer and the saturated half-space is derived,and the expression of the surface displacement in the saturated half-space of the overlying elastic layer is obtained.The composition of waves in soil under different water levels is studied in the wave number,and the effects of load velocity,frequency and saturated soil parameters on the vertical displacement of the ground are discussed in the spatial domain.It is found that the stratification caused by groundwater will produce reflected waves on the interface,thereby affecting the ground vibration response of the overlying elastic layer.When the water level is relatively close to the surface,the surface displacement is close to the saturated half space.And when the water level is relatively far from the surface,the impact of reflected waves on the surface decreases,and the displacement is close to the elastic half space.3.Coupling the elastic wave module and the poroelastic wave module in COMSOL,a saturated half-space model of the overlying elastic layer with a trench is established,that uses a perfectly matched layer to simulate the propagation of infinite-domain waves.The influence of water level changes on vibration isolation effect is discussed in the empty and filling trench,and it is found that some water levels will cause the vibration isolation effect to deteriorate due to the resonance of P wave.When the water level is close to the surface,the impact on the vibration isolation effect is relatively strong,and when the water level drops to a certain level,the impact is small.