铜尾砂和钨尾砂的抗剪强度及宏细观分析

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

铜矿和钨矿在经过开采和选矿过程后产生大量的尾砂,尾砂的抗剪强度直接影响到尾砂筑坝的稳定安全性和材料的创新利用。尾矿库现场取回尾砂的级配曲线不同于选矿产生的全尾砂,选用合适的尾砂抗剪强度参数以及对不同尾砂抗剪强度的比较和分析有助于评估尾矿库的溃坝安全性。为了深入研究铜、钨两种尾砂的抗剪强度及异同点,针对不同粒径范围的铜、钨尾砂进行了直剪试验、X射线衍射分析和扫描电镜分析。直剪试验结果表明,干燥尾砂表现出无黏性土的强度性质,相同粒组尺寸的铜尾砂抗剪强度要高于钨尾砂的抗剪强度;铜尾砂和钨尾砂在含水率为15%情况下的抗剪强度表现出一定的黏聚力,使其抗剪强度相对于干燥状态下提高了16.7%~83.8%;随着含水率从10%增加到20%,细粒钨尾砂的内摩擦角变化不大,含水量的增加使得钨尾砂的黏聚力较明显地减小并使得抗剪强度降低。X射线衍射分析结果显示铜尾砂和钨尾砂都以石英为主晶相,其余矿物成分大都是以硅酸盐为主的次生矿物;5000倍扫描电镜照片显示细粒尾砂颗粒的表面附着一定量的黏土矿物,黏土矿物的存在导致了尾砂抗剪强度随含水率增加而发生变化。

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 unclassifiedtailings 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.