Concerning the rare study on physico-mechanical properties of phosphogypsum

the relationship of water content with baking temperature and baking time

as well as the relationship of solubility with temperature is investigated by lots of experiments. According to specification of soil test

the tested water content of phosphogypsum increases with the increasingly baked temperature and baked time. In fact

the water content should be a constant

so the experimental method has to be improved. Phosphogypsum is suggested to test the water content under 55－60℃ for more than 36 hours. Through the experimental results

phosphogypsum has certain solubility

which decreases with the growing solution temperature. Because of the solution property

the distilled water must be substituted by the saturated phosphogypsum solution when the seepage experiments and triaxial compression tests are done. It is found that the coefficient of permeability in vertical direction is more than that in horizon direction from the seepage test results. And this property is different from the normal tailings. it is also found that phosphogypsum has obvious dilatancy when being sheared through the consolidated-drained triaxial compression tests. A conclusion can be drawn that the pore water pressure is minus when phosphogypsum specimen is damaged

and that the strain of damage is not sensitive with the confining pressure. Making use of the dilatancy of phosphogypsum

the safety of phosphogypsum dam can be forecasted theoretically by the pore water pressure monitoring system.