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  • 1. Apelqvist, Veronica
    et al.
    Apelqvist, Sandra
    Salvuppföljning: Mätning och analys av skillnaden i indrift före och efter skrotning2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this project was to follow up blasting at the development work of drifts by measuring the distance from a fixed point to the faces before and after scaling and then analyzes the data. LKAB Malmberget needs to follow up the blasting to improve and make the development of drifts more effective. The goals of the project have been to investigate if the length of the drill rods, drilling plan or the placement of faces affects the need for scaling. The work has involved a literature review of tunneling and its processes, a five-week field study at the development of drifts in LKAB Malmberget where the collection of data was done, analysis, comparing and finally documenting in report form. Development is the first step in the extraction of ore. Development involves the building of new fields and transport routes in the mine where the ore can be mined and transported. There are two types of drifts in the ore bodies, main gallery and cross cut. It is in the cross cuts the large-scale sub-level caving takes place, which LKAB is known for. At the development work, LKAB Malmberget is using the conventional cycle of blasting which includes drilling, charging, blasting, ventilation, excavation, scaling and reinforcement. At the drilling of the drifts there are three drilling rigs with two different lengths of the drill rods, 16 and 18 feet. In the western field, a rig with 18 foot rod is used and the eastern field has two rigs with both 16 and 18 foot. There are also two different types of drilling plans with different numbers of holes. The drilling plan with 76 holes is used on the western field and the drilling plan on the eastern field has fewer holes. The results of the project show that the need for scaling is greatest when using the 18 foot drill rods, which can be caused by abnormalities of the drill holes or a failed blasting where the rock was not thrown out in the drift. Since the drill holes are longer when using 18 foot drill rods there are also possible that air pockets are formed during the charging in the explosives which can result in an uneven and weak detonation. Further the results show that the need of scaling increases when the face is placed in ore which may be caused by the density. The ore has a higher density than waste rock which makes it harder to blast in ore. The difference in distance before and after scaling is more even for faces placed in ore, which may its base in the formation of a slice of ore closest to the face which is released more even then waste rock does under the scaling process. The drilling plan has no significant effect on the needed scaling because there is only a few holes difference in the drilling plans on the eastern and western field which otherwise is equal. If the dimensions of the profile may vary, there can be an effect on the need for scaling.

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