某尾矿坝毛细水带内的坝体材料物理力学特性研究

Study of physico-mechanical properties of dam body materials in capillary water fringe of a certain tailings dam

毛细水的存在将使尾矿坝坝体材料的物理力学特性发生较大变化,这种变化对尾矿坝的安全稳定势必产生影响,而国内外在此方面的研究工作却鲜有报道。为此,开展了某尾矿坝坝体材料现场取样、室内土工试验工作,并采用自制的毛细水带分层取样试验装置开展了长达6个月的毛细水上升测试工作,通过分层取样及土工试验,得到了毛细水带内尾矿砂的物理力学特性,进而系统地研究了毛细水带尾矿砂的含水率、重度、黏聚力、内摩擦角等物理力学指标随毛细水高度的变化特征。研究发现,毛细水带内尾矿砂的含水率和重度均随毛细高度而减小;黏聚力和内摩擦角的变化均随毛细高度和含水率呈先增大后减小的变化规律,其中内摩擦角的变化规律与以往相关研究所得结论并不完全相符,分析指出,这是由于毛细水和尾矿砂颗粒的表面特性所导致的;简要分析了抗剪强度随毛细高度的变化规律,发现其受毛细作用影响较大,呈先增大后减小的变化趋势。研究结果为坝体、边坡等工程的稳定性研究工作提供了一种新思路,为今后建立考虑毛细水作用下尾矿坝稳定性分析方法和理论奠定了基础。

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 oftailings 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.