| 1. |
- Johansson, Daniel, et al.
(författare)
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Dynamic blast compaction of some granular materials: small-scale tests and numerical modelling of a mining-related problem
- 2010
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Ingår i: International Journal of Mining and Mineral Engineering. - 1754-890X .- 1754-8918. ; 2:2, s. 79-100
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Tidskriftsartikel (refereegranskat)abstract
- Sub-Level Caving (SLC) is an important mass mining method, involving blasting of ore against granular material in the form of caving debris. The debris compaction due to blasting influences the caving process. Blasting tests were made on cylinders of magnetic mortar placed inside plastic cylinders and confined by packed granular material. By introducing the acoustic impedance between the mortar and the confining granular material, the compaction is found to depend on material, specific charge and physical properties of the debris with statistical analysis. The tests have shown to be a good input for numerical modelling of blast compaction.
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| 2. |
- Johansson, Daniel, et al.
(författare)
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Fragmentation in small-scale confined blasting
- 2011
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Ingår i: International Journal of Mining and Mineral Engineering. - 1754-890X .- 1754-8918. ; 3:1, s. 72-94
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Tidskriftsartikel (refereegranskat)abstract
- Design of sub-level blasting rounds and optimisation has become more important now when the sizes of the blasting rings get larger. Sufficient fragmentation is one of the key factors, and in confined blasting as in sub-level caving, this influences the mobilisation of the blasted ring. Model scale tests have been made to understand the mechanisms of rock breakage and therefore fragmentation under relatively confined conditions. By using the acoustic impedance between the blasted material and the confining debris, a relationship for fragmentation has been found depending on material, specific charge (powder factor) and physical properties of the debris. The results can be comparable with confined blasting in large scale.
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| 3. |
- Johansson, Daniel, et al.
(författare)
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Shock wave interactions in rock blasting : the use of short delays to improve fragmentation in model-scale
- 2013
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Ingår i: Rock Mechanics and Rock Engineering. - : Springer Science and Business Media LLC. - 0723-2632 .- 1434-453X. ; 46:1, s. 1-18
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Tidskriftsartikel (refereegranskat)abstract
- A series of detailed small-scale tests have been made to investigate the use of short delays to promote better fragmentation caused by shock wave interactions. The block design had a size of 650/660 × 205 × 300 mm (L × W × H) and two rows with five Ø 10-mm blastholes in each row. The spacing (S) and burden (B) were 110 and 70 mm, respectively, giving an S/B ratio of 1.6. The results showed no distinct differences or high improvements of the fragmentation when the delays were in the time range of interactions compared with no shock wave interactions. The decrease of x 50 (mean size) was around 20 % at a delay time ~1.1 ms/m burden compared with longer delays like 2 ms/m. A statistical analysis of the results has been made to evaluate the minimum at short delays and it is not significant
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| 4. |
- Ouchterlony, Finn, et al.
(författare)
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Fragmentation in production rounds and mill through-put in the Aitik copper mine : a summary of development projects 2002-2009
- 2013
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Ingår i: Rock Fragmentation by Blasting, FRAGBLAST 10. - Boca Raton, Fla. : CRC Press/Balkema. - 9780415621434 - 9780203387672 ; , s. 117-128
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Konferensbidrag (refereegranskat)abstract
- The Boliden Mineral Aitik mine has worked to increase the through-put in the primary AG mills together with Swebrec. A raised specific charge from 0.9 to 1.3 kg/m3 raised the throughput by nearly 7%. This was implemented in 2009. For two rounds Swebrec has mapped joints from 3D images to determine the rock mass factor and combined Split Desktop measurements with sieving of muck-pile samples to get the sieving curve of the muck pile, based on the Swebrec function. For a 3rd round such curves were fed into a crusher model and results compared with Online data. The crusher product can affect the mills by three mechanisms; a harder blasting that i) produces more fines that may pass the mill intact, ii) gives a finer crusher product which takes a shorter time to grind iii) increases the amount of larger stones that pass the crusher intact but have an increased grindability. All three must contribute to the increased mill through-put.
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| 5. |
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| 6. |
- Ouchterlony, Finn, et al.
(författare)
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Lessons from single-hole blasting in rock
- 2013
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Ingår i: Rock Fragmentation by Blasting. - Boca Raton, Fla. : CRC Press/Balkema. - 9780415621434 - 9780203387672 ; , s. 3-14
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Konferensbidrag (refereegranskat)
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| 7. |
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| 8. |
- Petropoulos, Nikolaos, et al.
(författare)
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Fragmentation under different confinement conditions and the burden behaviour : small scale tests
- 2012
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Ingår i: Measurement and Analysis of Blast Fragmentation. - Boca Raton, Fla. : CRC Press/Balkema. - 9780415621403 - 9780203387535 ; , s. 61-70
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Konferensbidrag (refereegranskat)abstract
- Small scale-tests have been performed on magnetic mortar blocks to investigate the influence of delay times, specific charge and firing pattern on fragmentation both when the burden is free and when confined by debris simulating the confined conditions of a SLC-blast ring and to study the burden behavior during blasting by implementing dynamic methods of measurements. The dimensions of the test blocks were 660 ×270 ×210 mm (L ×W ×H). Two different blast hole patterns, 2 rows with 5 holes with a burden of 70 mm (S/B ×1.6) and 3 rows with 7 holes with a burden of 58.3 mm (S/B ×1.4). A complete analysis regarding the influence of different delay times ranging from 0 to 4.1 ms/m of burden, different specific charges and different firing patterns on fragmentation has been made, based upon 22 blocks.
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| 9. |
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| 10. |
- Sanchidrián, José A, et al.
(författare)
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Performance of some distributions to describe rock fragmentation data
- 2012
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 53, s. 18-31
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Tidskriftsartikel (refereegranskat)abstract
- Ten functions (Weibull, Swebrec, Gilvarry, Grady and Lognormal, and their bi-component versions) are fitted to 448 sets of screened fragment size data from blasted and crushed rock. The ordinary least squares criterion has been used for the fits and two minimization techniques have been tested, in both cases running the problem repeatedly with different initial values of the unknown parameters in order to ensure a global minimum. There is a distinct behavior of errors across the passing range, which has been divided in four zones, coarse (>80%), central (80%–20%), fine (20%–2%) and very fine (<2%). The representation of fragmentation data by some of the distributions can be made with good accuracy in the coarse and central zones, with moderate accuracy in the fine zone and with considerably poor accuracy in the very fine zone. As expected, bi-component distributions generally perform better than the single-components, though there are important differences among them. Extended Swebrec is consistently the best fitting distribution in all zones, with maximum relative errors of less than 25% in the coarse, 15% in the central, and 50% in the fine zones. Bimodal Weibull, bimodal Gilvarry and bimodal Grady's errors are statistically equivalent to extended Swebrec's in the central and fine zones. In the very fine zone, relative errors have a high probability of being in excess of 100%, with maximum expected values being several times that, even for the best fitting functions in this zone. Swebrec is by far the best single component function in all zones, with errors comparable to the best bi-components in the coarse and central.
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