Abstract: The purpose of this study is to obtain the rule of tailings sand's matric suction varying with different water content. On the basis of particle gradation test of tailings sand, the matric suction in moisture absorption stage and dehumidification stage of tailings sand were tested respectively using contact filter paper method. Twelve groups of matric suction with a water content ranging from 9% to 40% were acquired. The soil-water characteristic curve (SWCC) of tailings sand in moisture absorption and dehumidification stages is established, and the variation characteristic of SWCC is analyzed. Results indicate that the tailings sand belongs to silty clay. The SWCC of tailings sand in a large suction range obtained by filter paper method approximates an inverted “S” shape. The SWCC of tailings sand can be divided into four stages. With the increase of water content, matric suction decreases in stages. The matric suction of tailings dam measured by filter paper method varies in a large range from 2 711.095 kPa to 22.459 kPa in the process of moisture absorption and from 28.205 kPa to 3 607.825 kPa in the process of dehumidification. The variation law of matric suction in the process of moisture absorption and dehumidification is basically the same. However, the change paths are different and obviously hysteretic. The matric suction in dehumidification process is higher than that in moisture absorption process.

Key words: tailings sand, matric suction, filter paper method, soil-water characteristic curve, moisture content