Mechanism And Application Of Abrupt Changes Of Hydraulic Conductivity On The Seawater-freshwater Interface

Hydraulic conductivity of aquifer is one of important hydrogeological parameters in the area of seawater intrusion. It not only depends on the characteristics of rock such as particle size, component, grain array and filling condition, but also depends on the physical character of permeating solution such as density and viscosity. The variation of aquifer's permeability has an important effect on the shape of fresh-salt water interface, transport and the extent of seawater intrusion. Therefore, it is a significative research for investigating the salinity's effect on hydraulic conductivity of aquifer in the freshwater-seawater interface.Physical and chemical character of aquifer media, colloid and water samples in the downstream of Dagu river is studied systemically. Based on that, this paper mainly studies the abrupt variation of permeability. Using the abrupt experiment and gradual experiment of salt-fresh water, the variation of hydraulic conductivity under different hydraulic field and chemical field is studied. The reason for variation of permeability is analyzed and different factors that have effect on the variation of permeability are discussed. Adopting the micro-sand-column, the influence of different water chemical and hydraulic conditions on the releasing process of clay in the seawater-freshwater interface is studied. Critical salt concentration, critical ionic strength and critical flow velocity for the particle release is determined. Finally, the control experiment of hydraulic conductivity is processed to investigate the variation of micro-structure of pore in the salt-fresh water's displacement and temporal and spacial variation law of permeability. On the basis of a series of researches above, the major conclusions presented in this paper can be summarized as follows:(1) In the process of mutual displacement between river water and seawater, it is distinct variation of hydraulic conductivity of aquifer media in the...