Abstract
A floating underground dam has been proposed as one of the promising means to increase the volume of water in freshwater lens. One of the most concerning things is residual salinity of groundwater while fresh water is infiltrating into underground. We conducted laboratory tracer tests for Ryukyu limestone as an example of Quaternary carbonate, using a microfocus X-ray CT to reveal its characteristics of mass transport. The results showed that large pores in this act as main flow paths of fluid flowing. In matrix part some flow paths were observed too. These results suggest that taking flow in matrix part into account is important to make a numerical model of Ryukyu limestone as distinguishing large pore and matrix.
