Tailings are the most fine grained mine waste generated due to mining and consists of crushed rock in the size ranges of sands, silts and clays depending on the ore processed. Due to the risk of high contents of metals, acids and soluble salts in the tailing a environmentally safe approach of disposal becomes imperative. Failures to retain tailings can and has in many cases led to both mechanical and chemical destruction in the sense of environmental pollution, destruction of infrastructure, health issues and loss of life.

Therefore, a better understanding of the geotechnical properties of the different tailings are needed in order to better plan and manage the tailings and their storage facilities. This report focuses on some of the mine waste from the Boliden mining area contained in the Hötjärn tailings facility. Specifically the hydraulic conductivity and compressibility characteristics of the tailings from the Kristineberg mine and the furnace slag from the Rönnskär smelters. The coarser sand fractions of the Kristineberg tailings are at times used as backfill material in the mines and the sample has therefore been separated in to three different Kristineberg based samples and one slag based sample.

In order to get an overview of the materials some basic geotechnical investigations (particle size distribution and particle density tests), constant head tests for hydraulic conductivity and oedometer tests to determine compressibility were carried out.

Results showed a clear difference in particle size distribution with a fines content spanning between approximately 25 and 50 percent. Furthermore hydraulic conductivity was shown to be dependent on dry density and material, decreasing with increasing density. Finally the unaltered Kristineberg tailings showed the largest strains whereas the Rönnskär slag showed smallest strains.

The results presented within this report constitute a god basis for further consolidation and seepage analyzes within the Hötjärn tailings facility.