泥沙颗粒表面电荷特性及其对干容重影响试验研究

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。

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

The potentiometric titration and dry-bulk density experiment was done using the sediment of different Ca2+ concentration in the Yellow River and the Yangtze River and some conclusions are given as following: ①The surface negative charge of sediment firstly unceasingly reduces and then tends stable with the increasing of the Ca2+ concentration;②The influence of the Ca2+ concentration on the dry-bulk density can be divided into three phases with the increasing of Ca2+ 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;③When the Ca2+ concentration is equal,the influence of sediment concentration on the dry-bulk density has different change with the increasing of the Ca2+ concentration;④As the Ca2+ 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 liter Ca2+ when its dry-bulk density gets the maximal value;And ⑤ the sediment electrostatic repulsion is different because of the dif erent surface negative charges in the different Ca2+ concentration,and the water film force is different,too.Both of two reasons show that the dry-bulk density reflects the above mentioned changes.