Study On The Effect Of Moisture Desorption-Absorption Cycie On The Physical And Mechaanical Properties Of Tailings Sand

Tailings will be in a state of moisture desorption-absorption cycle because of precipitation infiltration,vaporizaton and the rise and fall of phreatic level. This variation state can further affect the physical and mechanical properties' change mechanism of tailings in the cyclic dry-wet process, which is relate to the safety operation of the tailings dam. Therefore, this paper takes a tailings dam in hunan province as the research object and conducts research with the method of field sampling and indoor simulation test. Firstly, it tests the basic physical and mechanical parameters of tail ore. Then, it uses self-made stratified sampling test device to simulate the cyclic dry-wet process, and meanwhile analyzes the change of physical and mechanical parameters of tailling sand that has experienced the cyclic dry-wet process, in detail.Finally, with the combination of the basic principle of strength subtraction and the numeral simulation software ABAQUS, it analyzes the stability of the tailing dam that has experienced the cyclic dry-wet process. In this paper, the main research results and conclusions are as follows:(1) In the process of dry-wet cycling test, the same moisture content corresponded to different matrix suction and the soil-water characteristic curve of tailling ore appeared the hysteresis effect. However, thisvariation was biggest in the first three times of cyclic dry-wet process.With the continuation of dry-wet circulation process, the soil-water characteristic curve tends to be stable gradually.(2) In the process of test, the soil-water characteristic curves of tailling sand that under the different times of desorption-absorption cycle are fitted. And the prediction model of soil-water characteristic curve under the action of desorption-absorption cycle has been gotted.(3) Under the influence of desorption-absorption cycle, the shear strength of tailling sand decrease gradually with the increase of number of dry-wet cycle. Meanwhile, the shear strength of the tailling sand tends to stable after 4 cycles. Intensity changes is mainly manifested in the variation of the internal friction angle of strength parameters and the cohesion. As the dry-wet cycle gets under way, the internal friction angle of tailling sand and the cohesion decreases gradually and finally became stable. However, the attenuating range of internal friction angle is bigger than the attenuating range of cohesion.(4) Under the action of desorption-absorption circulation, the shear strength of tailling sand with matrix suction of 10 Kpa is greater than the shear strength with matrix suction of 15 Kpa. With the increase of number of dry-wet cycle, the impact that matrix suction has on the increase and decrease of shear strength will change under the high stress state.(5) Along with the desorption-absorption circulation, the safety coefficient of tailings dam decreases gradually. In the first three times of desorption-absorption circulation, the safety coefficient of tailings dam attenuates quickly. Later on, the attenuation speed becomes stable gradually. In the whole process of dry-wet circulation, the stability coefficient of taillings dam drops from 2.05 to 1.70 and the overall decline reached 17.1%, which demonstrates that thedesorption-absorption circulation can influence the stability of the tailing dam.