SHEAR STRENGTH AND MACRO-MICRO ANALYSIS OF COPPER TAILINGS AND TUNGSTEN TAILINGS

A large amount of tailings are produced after mining and beneficiation process of copper ore and tungsten ore. The stability safety of tailing dams largely depends on the shear strength characteristics of tailings. And the shear strength properties can also determine the innovative utilization of the tailings in future. The gradation curve of tailings obtained by means of tailing pond site sampling is different from the gradation curve of unclassified tailings produced by beneficiation process of ores. Selection of suitable shear strength parameters of tailings and comparative analysis of the shear strength of different tailings can be helpful to evaluate the dam break safety of tailings pond. In order to study the shear strength characteristics of copper tailings and tungsten tailings as well as the main differences and similarities between two kinds of tailings, a series of direct shear tests are carried out for copper tailings and tungsten tailings with different particle size ranges. Besides, X diffraction analysis and scanning electron microscope(SEM)analysis are conducted to study the intrinsic micro mechanism. The direct shear testing results demonstrate that dry copper tailings and dry tungsten tailings behave the strength properties of cohesionless soil. In the case of the same particle size range condition, the shear strength of the copper tailings is higher than that of the tungsten tailings. Both the copper tailings and tungsten tailings show a certain value of cohesion when the water content is 15%. The shear strength of hydrated tailings with water content of 15% increases by 16.7%~83.8% relative to the dry condition. With the increase of water content from 10% to 20%, no obvious change is shown to the internal friction angle of fine grained tungsten tailings. However, the cohesion decreases obviously with the increase of water content, which reduces the shear strength of tailings. The results of X-ray diffraction analysis show that both copper tailings and tungsten tailings are mainly quartz crystal phases and the other mineral components are mostly silicate secondary minerals. The 5000 times magnified SEM photos display that a certain amount of clay minerals can be observed on the surface of fine tailings particles. It is due to the effect of clay minerals that the shear strength of tailings changes with the increase of water content.