Numerisk simulering av en uppströmsbyggd gruvdamm : Med finita elementprogrammet PLAXIS 2D

The waste materials coming from mining processes are called tailings and are usually contaminated with environmentally unfriendly substances. These requires disposition of the tailings during safe conditions. Swedish mines are usually utilizing the topography of nature in combination with embankment dams to store their tailings, and the Aitik copper mine is no exception. The start dike is an embankment dam built with an impermeable till core. It is extended by more permeable materials with both the upstream and the downstream method. The extension of the embankment dams are constructed continuously as the mine produces more and more tailings. Therefore it is of interest to simulate the dam future stability in order to maintain the dam safety. GruvRIDAS recommends a factor of safety higher than 1.5 for dams during normal conditions. A global factor of safety has been obtained by simulating the dams future raisings in the finite element program, PLAXIS 2D.The simulations performed in this Master’s Thesis are based on a typical annual cycle. These yearly cycles should correspond to the real activities done at the dam cross section. These activities represent different clauses, such as construction of a new dike, resting periods, spigotting periods and winter periods. Resting periods and winter periods represent periods where the dam section is undisturbed and only consolidation of the soil takes place. The spigotting periods represent when tailings are distributed into the impoundments. During the winter periods berms are added on the downstream slope in order to have factors of safety greater than 1.5 during next dike construction.In earlier studies the stability of the dam has been simulated during the year 2014 to 2024. This thesis covers simulations of the dam safety until year 2034. Real life conditions have been created by using a geometric model based on the dam cross-section and material properties obtained from geotechnical investigations. In this thesis annual dikes risings at the studied dam section has been simulated in PLAXIS 2D. The geometry was divided into finite elements where stresses and deformations were calculated. These stresses and deformations have been used in order to analyze the dam stability. Annual simulations during 2014 to 2024 have been made and compared with earlier stability studies. The comparison of the results from two studies indicated only small deviations and not large enough to prevent further simulations for the time span between year 2024 and year 2034.The stability simulations resulted in factors of safety below the recommended value when no berms were added on the downstream side of the dam. The factors of safety indicated a decreasing trend and by adding berm on the downstream side of the dam the factors of safety were increased to values above the recommended values. It was also shown that different sizes of rockfill berms had to be applied on the downstream slope in order to prevent potential slip surfaces in the slope.Validerat; 20150625 (global_studentproject_submitter