Abstract
A large quantity of sand is needed as material for filtering and draining in earth dam. However, no natural sand exist except for sea sand which consists of dead coral polyp in the Okinawa area. So crushed sand of limestone is used for part of the public works projects. Both types of calcareous sand were dissolved in water dissolving CO2, because it consists of CaCO3.
The present paper reports on a solution of calcareous sand used as filtering and draining material. The solution of calcareous sand was investigated through gauging the sand mass and chemical analysis of Ca2+, and by dissolving in tap water.
The results are summarized as follows.
1) A calcareous sand solution is related to CO2 regarding tap water, temperature, velocity of passing water and length of sample.
2) A solution rate by tap water with a 5. 9×10-3cm/s passing velocity was about 15%/year in coral sand and 5-6%/year in limestone sand.
3) In carbonated water, containing CO2 100 times as much that in tap water, it took about 150 days in coral sand and 360 days in limestone sand to be completely dissolved.
Since both types sands are soluble in water, it is concluded that calcareous sand should not be used inside of earth dams.
