Experimental Study On The Migration Mechanism Of Water And Salt In Saltwater Leakage Process

The ground water of quaternary in the North China Plain has double structure of"under the salty light". Due to long-term exploitation of the deep water, that leads to thehead of the layer dropping substantially, and makes the whole shallow salty water downreplace the previous state of the fresh water. The flow accounts for about40%～70%inthe gross recovery of the groundwater in north China plain. In the leakage deep waterwhether being salinization is important. Solving this problem requires experiments of theeffect and mechanism of water salt movement in the leakage.The clay is selected in Tangshan urban and coastal. To different hydraulic gradient,different experiments of disturbed soil penetration and undisturbed soil penetration arecarried out with salt (10g/L). The experiment of undisturbed soil is designed to simulatethe salt water in the wild over-exploited state during the leakage. Regularly monitor theconcentration of Cl-and Na+in water, then obtain the breakthrough curves. Test theadsorption capacity of the soil on ion exchange capacity by static adsorption experiment.Simultaneity, scanning electron microscopy, X-ray diffraction, mercury intrusion and thewhole rock analysis are taken to analyze the microscopic structure, minerals and elements.The results show that outlet Na+concentration to the initial ratio (C/C0) is less thanthe Cl-one; the inlet conductivity shows an upward trend and concentration in thedisturbed soil experiment; In the undisturbed soil experiment, the concentration ofsolution into water shows enrichment, Na+and Cl-concentration to initial concentration(C/C0) was1.4times, but at the outlet the changes of Na+and Cl-are almostsimultaneously, ratio (C/C0) basically stable at1.0after the experimental stability.The disturbed soil test results show that the larger head difference the faster salttransport; concentration and separation prove that the clay has "membrane effect".Undisturbed soil test shows greater pressure, smaller pore and higher osmotic pressure,influence the "membrane effect" worse and weaker. The comprehensive analysis showsthat, clay has membrane effect, but the membrane reflection coefficient low.