泥沙颗粒表面电荷特性及其对干容重影响试验研究

Experimental study on surface charge properties of sediment particles and their effect on dry-bulk density

采用黄河及长江中的沙样在不同Ca2+浓度下分别进行电位滴定试验和干容重试验,得到以下结论:①随Ca2+浓度的增加,泥沙颗粒表面负电荷先不断减少然后趋于不变。②Ca2+对泥沙淤积干容重的影响可分为三个阶段:第一阶段干容重减小;第二阶段增加并达到最大值;第三阶段减小最后趋于不变。③在Ca2+浓度相同条件下,泥沙浓度对淤积干容重的影响根据所加Ca2+浓度不同也呈现不同的变化。④Ca2+浓度、泥沙浓度相同时,中值粒径越大干容重越大,且中值粒径大的泥沙干容重达到最大值所需Ca2+少。⑤在不同Ca2+浓度下泥沙颗粒由于表面电荷不同造成静电斥力不同,同时表面水膜作用力也不同,二者共同作用使得干容重体现不同的变化。

The potentiometric titration and dry-bulk density experiment was done using the sediment of different Ca^2＋ concentration in the Yellow River and the Yangtze River and some conclusions are given as following： （1）The surface negative charge of sediment firstly unceasingly reduces and then tends stable with the increasing of the Ca^2＋ concentration; （2）The influence of theCa^2＋ concentration on the dry-bulk density can be divided into three phases with the increasing of Ca^2＋ concentration： the first phase is that the dry-bulk density reduces, the second one is that the dry-bulk density increases and gets the maximal value, and the third one is that the dry-bulk density reduces and finally doesn＇t change; （3）When the Ca^2＋ concentration is equal, the influence of sediment concentration on the dry-bulk density has different change with the increasing of the Ca^2＋ concentration; （4）As the Ca^2＋ concentration and the sediment concentration are the same, the dry-bulk density will get bigger when the sediment median size increases, and the sand whose median size is big needs litter Ca^2＋ when its dry-bulk density gets the maximal value; And （5）the sediment electrostatic repulsion is different because of the different surface negative charges in the different Ca^2＋concentration, and the water film force is different, too. Both of two reasons show that the dry-bulk density reflects the above-mentioned changes.