The physico-mechanical properties of tailings dam material will be changed by capillary water

which will effect on the stability of tailings dam. The research on this field is barely reported at home and abroad. Therefore

in-situ sampling and laboratory geotechnical experiments on tailings dam material are conducted for testing its physical properties

and the rising test of capillary water is carried out about 6 months by the self-designed layered sampling device for capillary fringe; and the physico-mechanical properties of tailings sand in capillary water fringe are gained by layered sampling and soil testing. Furthermore

the variation characteristics of physico-mechanical indexes such as water content

gravity density

cohesion

internal friction angle and shear strength with the height of capillary water have been systematically studied. The results show that water content and gravity density decreased with the height of capillary water. The relationships of cohesion and internal friction angle with the height and water content increases firstly and then decreases. However

the relationship of internal friction angle with water content is different from the traditional conclusion that the relationship is decreasing with water content. This difference is caused by surface properties of the tailings particles which are different from that of sands. The surface of tailings particles is dirtier than that of sands and is covered by mineral and something else which is soluble in water. The research results also show that the effect of capillarity on shear strength is great

and the relationship of shear strength with the capillary height increases firstly and then decreases. As we known

the gravity is one of major causes of tailings dam failure. In a real tailings pond

there is full of industrial wastewater which has bigger surface tension than pure water

and the bigger surface tension will cause higher capillary water in tailings dam. In fact

the capillary water will result in weight gain of tailings dam which is danger to the stability of tailings dam. Therefore

it is more important to analyzing the stability of tailings dam by researching on the physico-mechanical properties of dam body materials in capillary water fringe of tailings dam. This research will put forward a new idea to the dam and slope engineering

and laid a foundation for establishing a new method and theory to analyzing stability of tailings dam by considering the role of capillarity.