Effekten av inspänningen på fragmentering samt dynamiska mätningar försättningens rörelser: Resultat från småskaliga sprängförsök
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Every mining method, underground or surface is adopted based on economical and geological criteria. The tests in this thesis have been conducted based on Sub - level caving mining method which is used by LKAB mines. The aim of these tests was to investigate the fragmentation in different long delay times and conditions, in small scale tests. The second task is to investigate the burden behavior under confined conditions. There were two different designs. The first design included a magnetic mortar with 5 holes and specific charge 2.56 kg/m3. The second design included a magnetic mortar with the same properties as in the first design but with a different specific charge 4.16 kg/m3. The dimensions of the blocks were 110x270x210 mm and the diameter of the holes was Ø 11. The common point in both designs was the ratio of spacing to burden which was kept stable at 1.57 (110/70 ≈ 82.5/52.33). The correlation between the two different designs has been done based on the delay time. The delay time is adjusted in that way so that the results from the two designs would be compatible. The results show an improvement in fragmentation for long delay by 32.94 % from 110 μsec to 218 μsec. Additionally, they show the difference between V – shape and sequential firing pattern which is 46 % under confined conditions. The second task of the thesis was to investigate the burden movement and velocity. Three different methods have been implemented; draw wire, accelerometers and nails. The draw wire was slow to give good results probably due to high accelerations and some inertia issues. The accelerometers did not show the burden movement because the signal of the burden movement was hidden behind the reflections of the waves. The nails gave results that are good for analysis. Finally, the burden velocity had a peak value of 22 m/s and a maximum compaction of 14.3 mm. The value of compaction varies depending on different cases. The given compaction corresponded to V – shape firing pattern. However, for the sequential firing pattern the compaction was 12.6 mm, something that is reasonable due to different movement of the burden.
Place, publisher, year, edition, pages
2011. , 173 p.
Technology, fragmentation, small scale tests, burden velocity, burden movement, compaction, confined/unconfined blasting
IdentifiersURN: urn:nbn:se:ltu:diva-58261Local ID: ed75e2e5-6fcb-4c21-955b-5434f1636f58OAI: oai:DiVA.org:ltu-58261DiVA: diva2:1031649
Subject / course
Student thesis, at least 30 credits
Civil Engineering, master's level
Validerat; 20110629 (anonymous)2016-10-042016-10-04Bibliographically approved