磷石膏物理力学特性初探

通过大量的室内试验，研究了磷石膏的烘烤温度与含水率的关系、烘烤时间与含水率关系、溶解度与温度关系。按土工试验规范进行试验，测得磷石膏的含水率随着烘烤温度的升高而增加，也随着烘烤时间的增长而增加，但是含水率应该是一个恒定的指标，所以磷石膏的含水率的测定不能按照现行规范进行，必须加以改进。建议在55～60℃条件下烘烤36 h或更长时间来测定磷石膏的含水率。从试验还可以得知磷石膏有一定的溶解度，且其溶解度随着温度的升高而降低。也正是由于磷石膏的溶解特性，所以在进行渗透试验和三轴剪切试验时要使用室温条件下的饱和磷石膏溶液替代水，从渗透试验结果来看，磷石膏坝渗透特性不同于一般的尾矿坝，其垂直渗透系数要大于水平渗透系数。从磷石膏的固结不排水三轴剪切试验可知，磷石膏是一种有明显的剪胀性的材料，在剪切条件下其破坏发生在孔隙水压力为负的情况下，且其破坏时的应变受围压的影响不明显。利用磷石膏的剪切破坏发生在负孔压的这一特性，理论上可以通过坝体内孔压变化的监测来预测磷石膏坝的安全性。

Study on physico-mechanical characteristics of phosphogypsum

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.