Experiment on tailings capillary characteristics based on particle size effect

Using a self-developed system for online monitoring capillary rise test (OM-CRT) to explore the effect characteristics of tailings particle size on capillary water rise of tailings dam, the whole process of capillary water rise was tested according to the tail fine sand, the tail silty sand and the tail silty soil of different particle sizes, the relation curves and fitting equations of the rise height, rise speed and time of capillary water in tailings are obtained, and the variation rule and influencing factors of water content in capillary zone in different profiles with time were analyzed. The results show that the wetting front and time is logarithmic relationship when the tailings capillary water rises. The capillary water rises quickly in early trial, but with the test time increasing, the capillary water rises slowly and stops rising eventually. Therefore, the height and velocity of capillary water rise are negatively correlated with the tailings particle size. The relation between the instantaneous water content change and time in different profiles is similar to the characteristic curve of water and soil, showing the shape of 'S'. The moisture content in three cylinders decreases with the height increasing. The moisture content in the capillary zone of the bottom of the tail silty soil sample is 23.77%, which forms a stable saturated capillary band of 300 mm. Through the relation between capillary diameter and tailings particle size is established, and the relation between particle size and capillary water rising height is further deduced. The capillary water rising test proves the existence of suction and capillary action in tailings and further verifies the principle of interface action. The research results can lay a foundation for the dam stability analysis method and theory under the influence of capillarity, and provide a new approach for the stability study of slope engineering. © 2020, Science Press. All right reserved.