Study On The Particle Transport And Deposition In Saturated Porous Media

Particle transport and deposition in saturated porous media play an important role in pollutant purification, nuclear waste disposal, oil exploration and internal erosion of hydraulic structures. According to the correction of the classic one-dimensional particle filter model, this paper obtained analytical solutions for different injection methods and containing sources and sinks. Secondly, the three-dimensional models which have considered the dispersion effect and particle release effect were established, so the study of particle transport extends to three-dimensional space. The solutions may be used for predicting particle concentration, verification of more complicated numerical model and determination test parameters. On the other hand, according to the soil column test, the effect of seepage velocity, seepage direction, particle concentration and particle size distribution on particle transport and deposition have been studied. Besides, the effects of increment of seepage velocity and particle size on the release of deposition particle have been studied. The main contents include:(1) In the present study, the porous media regarded as saturated, homogeneous and isotropic medium. Analytical solutions of corrected convection-dispersion models that takes into account dispersive flux on the deposition kinetic was obtained, including four types (short time injection, instantaneous injection, concentration decay injection and containing sources and sinks). The studies show that, the peak value of concentration decreases with increasing time, deposition rate, distance or the width of the source. Furthermore, these observations suggest that particle concentration affected by dispersive flux on the deposition kinetic equation, and the effect is strongly coupled to conditions.(2) Based on the one dimensional model, three-dimensional models which have consider the dispersion effect and particle release effect was established. General solutions were derived with the help of Laplace and Fourier transforms. According to the general solutions, specific solutions (instantaneous injected and periodically injected) are presented for point and areal inflow regions. Finally, the analytical solution for point source under instantaneous injection was taken as example of specific solutions, and a detailed discussion of the various transport parameters was conducted. The range of low concentration contour increases with increasing time and high concentration contour decreases with increasing time. The concentration contours decrease with increasing deposition rate. The concentration contours increase with increasing release coefficient for the three-dimensional model which have consider particle release effect.(3) Experiments were conducted to investigate the effects of particle size, particle concentration, hydrodynamic force on the transport and deposition of particle in saturated porous media. Four different size and four different concentration experimental series were performed, which series including three different seepage velocities experiment. The studies show that, particle turbidity can represent particle concentration of certain size and shape particle. The peak concentration of effluent increases with the increasing seepage velocity for the same particle size. Besides, there exists a critical concentration for particles under a constant flow velocity, the critical concentration of particles increases with the increasing seepage velocity.(4) In order to study the effect of particle size and seepage velocity on the release of deposited particle,4different suspended particle concentrations have been studied under3flow velocities in columns of saturated porous media. Two different velocity increment series which including two different particle size were performed. Besides, the effects of flow velocity increment and particle size on the release of deposited particle have been studied. Finally, the relationship between the amount of deposited particle and the depth was quantitatively analyzed. Generally, the release amount of small median particle size particle is greater than larger median particle size particle. The characteristics of the deposited particle are larger dependent on flow velocity increment.(5) Experiments were conducted to investigate the coupled effects of flow rate, flow direction, and particle size distribution on the transport and deposition of particle in saturated porous media. Three experimental series were performed, including downward flow, horizontal flow and upward flow. The breakthrough curves are well described by analytical solutions of a corrected convection-dispersion model. The flow direction is shown to be significant factors affecting the dispersivity of particle, especially in downward flow. Besides, the deposition rate decreases and the recovery rate increases with increasing flow rate. Furthermore, the particle deposition is affected by the median diameters or monodisperse index of particle.