Field damage investigation and evaluation of numerical model using the collected data at Kemi Mine

University essay from Luleå tekniska universitet/Institutionen för samhällsbyggnad och naturresurser

Abstract: This Master´s Thesis studies the applicability of existing numerical model to predict the conditions in the drifts at the mine. Damage mapping, covering the existing production levels, has been carried out to study the condition of the surface support, i.e. shotcrete, mesh and rock bolts to quantify the amount of deformation visible in the tunnels. Irregularities in the floor levels were also mapped. The rock support applied varies between different areas, from only a layer of shotcrete to areas where shotcrete, mesh and cable bolts are applied sequentially. The large amount of support in some regions is required because of high in situ rock stresses in Kemi Mine. The geological conditions are challenging, with large local variation making efficient supporting and damage prediction difficult. Access drifts at the mine have varying service times, on average 6 years, which is a long time in a difficult environment. The results from this work are a mine specific damage classification, used in the mapping to capture the range of damages seen on site. A reoccurrence of same areas showing damages on several production levels is noted. Digitized versions of the damage maps were made and these have been compared to simulation results. The comparisons were made to plots of deviatoric strain, deviatoric stress and total displacement. Based on the work done during this project it can be concluded that the studied parameters have varying levels of agreement with the drifts, both when comparing the levels with each other and the results in the same level between spring and autumn. The best agreement is found with the deviatoric strain increment and the yielded elements. Rock mechanics and geological reasons for the variations seen between the mapping results and the simulations results can be further studied in the future, as can the alternatives for increasing the accuracy through changes in the numerical model or model type used for comparison.

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