| Summary: | In mining production, the refining process generates a fine-grained waste rock, called tailings. Tailings and process water is pumped or conducted to a deposit. Usually the deposit is a tailings dam, where the tailings are settled. Though this disposal method is widely used, it has some disadvantages related to the dammed water. In order to reduce the risks, tailings can be disposed under drained conditions with the use of seepage dams. The main issue of a seepage dam will be; filter the tailings and drain the water away. When tailings are disposed under drained conditions the opportunities will be raised to dispose tailings on heights. This provides landscaping possibilities. If waste rock can be used when seepage dams are built, this method will have some economical advantages.In order to find an optimal design of seepage dams with proper performance a number of tests have been carried at LKAB in Kiruna. The tests were accomplished during the summer 2001 in Kiruna. The test plant was set up with three cells with three seepage dams. One seepage dam was built of a fine-grained waste rock originating from mining activities in Kiruna and two seepage dams were constructed with a filter layer made of two different geotextiles. As a support layer a coarse-grained waste rock were used. The size of each cell was 10 * 20 * 2 m3. The filtration and the drainage capacity were measured. A laboratory test preceded the field test where the hydraulic conductivity was measured in two different types of fine grained waste rock.Slurry containing water and tailings was pumped into the test plant with the flow of 6 l/s. The concentration of solids was approximately 35 % by mass. In general, the filtration capacities were high in all seepage dams and, in particular, the seepage dam that was built of fine-grained waste rock. Almost 100 % of all particles were filtrated by the seepage dams. The drainage capacity was measured with piezometers, in one of the cells. They were placed at different depths near the seepage dam. Measured ...
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