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Navarro, J., Schunnesson, H., Ghosh, R., Segarra, P., Johansson, D. & Sanchidrián, J. Á. (2019). Application of drill-monitoring for chargeability assessment in sublevel caving. International Journal of Rock Mechanics And Mining Sciences, 119, 180-192
Open this publication in new window or tab >>Application of drill-monitoring for chargeability assessment in sublevel caving
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2019 (English)In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 119, p. 180-192Article in journal (Refereed) Published
Abstract [en]

Currently, the charging procedure for sublevel caving mining is carried out with no prior information of the rock mass condition. Thus, engineers are blindsided to unexpected rock conditions and ill-prepared to address issues associated with collapsing boreholes. This results on charging problems and, as consequence, bad fragmentation of the rock after blasting which difficult ore loading and transportation as the gravity flow of the rock is reduced.

This paper builds up the work done by Ghosh et al. (IJRMMS, 2018), to classify the geotechnical rock condition into five classes (solid rock, fractured rock, cave-in, minor and major cavity). From it, two applications based on the Measure While Drilling (MWD) technique have been developed: one for geotechnical rock condition of orebodies and the other for predicting the risk of collapse in boreholes. The work of Ghosh et al. has been improved into a geotechnical rock condition block model to simplify the quantitative assessment and automatic recognition of rock trends. A thorough correction of the MWD parameters has been also applied to minimize external influences other than the rock mass. From it, the risk of borehole collapses model has been developed by comparing different combinations of the geotechnical rock condition block-model with the charging length of 102 production fan-holes. The assessment of the number of collapsed and non-collapsed blastholes and the charging length/blasthole length ratio has been used to assign high, medium or low risk of collapse to each combination. The results predict collapses in the first half of the fan-holes for the high risk, collapses in the second half of the fan-hole for the medium risk and no collapses along the hole for the non-risk holes. The two models have been applied in large scale for two orebodies in the Malmberget mine, Sweden, which comprises 20 drifts and 5060 fan shape long-holes.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Rock mass condition, Underground blasting, Measurement while drilling (MWD), Block model, Explosives
National Category
Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-74969 (URN)10.1016/j.ijrmms.2019.03.026 (DOI)000472023100018 ()2-s2.0-85065716586 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-25 (johcin)

Available from: 2019-06-25 Created: 2019-06-25 Last updated: 2019-07-10Bibliographically approved
van Eldert, J., Schunnesson, H., Johansson, D. & Saiang, D. (2019). Application of Measurement While Drilling Technology to Predict Rock Mass Quality and Rock Support for Tunnelling. Rock Mechanics and Rock Engineering
Open this publication in new window or tab >>Application of Measurement While Drilling Technology to Predict Rock Mass Quality and Rock Support for Tunnelling
2019 (English)In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453XArticle in journal (Refereed) Epub ahead of print
Abstract [en]

A tunnelling project is normally initiated with a site investigation to determine the in situ rock mass conditions and to generate the basis for the tunnel design and rock support. However, since site investigations often are based on limited information (surface mapping, geophysical profiles, few bore holes, etc.), the estimation of the rock mass conditions may contain inaccuracies, resulting in underestimating the required rock support. The study hypothesised that these inaccuracies could be reduced using Measurement While Drilling (MWD) technology to assist in the decision-making process. A case study of two tunnels in the Stockholm bypass found the rock mass quality was severely overestimated by the site investigation; more than 45% of the investigated sections had a lower rock mass quality than expected. MWD data were recorded in 25 m grout holes and 6 m blast holes. The MWD data were normalised so that the long grout holes with larger hole diameters and the shorter blast holes with smaller hole diameters gave similar results. With normalised MWD data, it was possible to mimic the tunnel contour mapping; results showed good correlation with mapped Q-value and installed rock support. MWD technology can improve the accuracy of forecasting the rock mass ahead of the face. It can bridge the information gap between the early, somewhat uncertain geotechnical site investigation and the geological mapping done after excavation to optimise rock support.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Measurement while drilling (MWD), Rock mass investigation, Tunnelling, Rock mass quality, Rock support, Drill and blast technology
National Category
Mineral and Mine Engineering Infrastructure Engineering Construction Management Geotechnical Engineering Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-76382 (URN)10.1007/s00603-019-01979-2 (DOI)
Funder
Rock Engineering Research Foundation (BeFo), 344
Available from: 2019-10-14 Created: 2019-10-14 Last updated: 2019-10-15
Ittner, H., Olsson, M., Johansson, D. & Schunnesson, H. (2019). Multivariate evaluation of blast damage from emulsion explosives in tunnels excavated in crystalline rock. Tunnelling and Underground Space Technology, 85, 331-339
Open this publication in new window or tab >>Multivariate evaluation of blast damage from emulsion explosives in tunnels excavated in crystalline rock
2019 (English)In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 85, p. 331-339Article in journal (Refereed) Published
Abstract [en]

Blast damage in tunnels is usually regulated in Swedish infrastructure contracts as it can influence the quality and lifecycle cost for tunneling projects. The topic is important for underground constructions with a long operation period such as tunnels for public transport, permanent access tunnels in mines or underground repositories for nuclear waste. This paper aims to evaluate the influence of design and geology variables on the resulting blast fracture length and frequency by means of multivariate data analysis. The analysis was based on data from five field investigations carried out at tunnel sites in Sweden and Finland where emulsion explosives were used. Data was compiled and analyzed using Principal Component Analysis (PCA). Charge concentration was found to be the most influential design variable and hole spacing had limited influence on blast fracturing. Results from the PCA suggest that blast fractures length could be dependent also on geology and natural fractures. Three main groups of fracture patterns were identified, one group with relatively few and short blast fractures, a group with several longer blast fractures and a group with few or a single long blast fracture. The result shows differences in fracture length between the column and bottom charge part of the contour holes, with blast fracture lengths up to approx. 40 cm for the column charge and up to approx. 60 cm for the bottom charge.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Blasting, Blast damage, Emulsion explosives, Mechanized charging, Principal Component Analysis
National Category
Geotechnical Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-67454 (URN)10.1016/j.tust.2018.12.021 (DOI)000457512000031 ()2-s2.0-85059473074 (Scopus ID)
Funder
Rock Engineering Research Foundation (BeFo)
Note

Validerad;2019;Nivå 2;2019-01-10 (svasva)

Available from: 2018-02-01 Created: 2018-02-01 Last updated: 2019-04-23Bibliographically approved
Yi, C., Nyberg, U. & Johansson, D. (2018). Calibration and Validation of Reactive Flow Model Parameters for an emulsion explosive. In: : . Paper presented at 12th International Symposium on Rock Fragmentation by Blasting, Fragblast 12, Luleå, Sweden on June 9-15.
Open this publication in new window or tab >>Calibration and Validation of Reactive Flow Model Parameters for an emulsion explosive
2018 (English)Conference paper, Published paper (Refereed)
National Category
Engineering and Technology Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-69773 (URN)
Conference
12th International Symposium on Rock Fragmentation by Blasting, Fragblast 12, Luleå, Sweden on June 9-15
Available from: 2018-06-21 Created: 2018-06-21 Last updated: 2018-06-27
Petropoulos, N., Wimmer, M., Johansson, D. & Nordlund, E. (2018). Compaction of confining materials in pillar blast tests. Rock Mechanics and Rock Engineering, 51(6), 1907-1919
Open this publication in new window or tab >>Compaction of confining materials in pillar blast tests
2018 (English)In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 51, no 6, p. 1907-1919Article in journal (Refereed) Published
Abstract [en]

Two confined pillar tests were conducted at the Kiirunavaara mine to investigate the degree of compaction of three materials, i.e., 0–32-mm backfilled material, a blend of ore and waste material and caved material. Two blastholes were drilled parallel to each pillar wall, and several measurement holes were drilled in between the blastholes through each pillar. Both the measurement holes and backfilled materials, except the caved material, were instrumented. Two types of measurements were taken: dynamic measurements with accelerometers, and static measurements which considered the location of the instrumentation pre- and post-blast. Dynamic measurements involved the burden movement and the confining material behavior, and static measurements contained the final location of sensors inside and the angle of repose of the confining material. The results showed that the size distribution of the confining material affects its behavior under dynamic loading. The backfilled materials showed an apparent cohesion forming an agglomeration on the surface of the blasted burden. The burden moved as one slab due to simultaneous detonation. A gap was formed between the blasted burden and the new face. This gap was partially filled with burden erosion material which was finer fragmented than the blasted burden material.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Compaction, burden movement, pillar tests, sublevel caving, confined blasting
National Category
Mineral and Mine Engineering Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-67850 (URN)10.1007/s00603-018-1447-8 (DOI)000433195900016 ()2-s2.0-85047517598 (Scopus ID)
Projects
Improved understanding of sublevel blasting – Determination of the extent of the compacted zone, its properties and the effects on caving
Note

Validerad;2018;Nivå 2;2018-06-01 (rokbeg)

Available from: 2018-03-06 Created: 2018-03-06 Last updated: 2018-08-27Bibliographically approved
Yi, C., Johansson, D. & Greberg, J. (2018). Effects of in-situ stresses on the fracturing of rock by blasting. Computers and geotechnics, 104, 321-330
Open this publication in new window or tab >>Effects of in-situ stresses on the fracturing of rock by blasting
2018 (English)In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 104, p. 321-330Article in journal (Refereed) Published
Abstract [en]

Blasting is widely applied in deep rock excavation. The effect of in-situ stresses on the fracturing of rock due to blasting was investigated. A theoretical model was used to explain the effect mechanism of in-situ stresses on crack propagation due to blasting. Four cases with different in-situ stress conditions were numerically investigated. The numerical results indicate that the crack propagation is governed by the blast load in the vicinity of the blasthole while the high in-situ stresses can influence the crack propagation in the far-field. The crack propagation trends towards the direction in which the high initial pressure is applied.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Blasting, In-situ stresses, Crack propagation
National Category
Other Civil Engineering
Research subject
Mining and Rock Engineering; Centre - Swedish Blasting Research Centre (SWEBREC)
Identifiers
urn:nbn:se:ltu:diva-67060 (URN)10.1016/j.compgeo.2017.12.004 (DOI)000449125200029 ()2-s2.0-85038407140 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-19 (johcin)

Available from: 2017-12-19 Created: 2017-12-19 Last updated: 2019-03-26Bibliographically approved
Yi, C., Johansson, D. & Nyberg, U. (2018). Numerical investigation for timing effects on fragmentation based on a coupled FEM-BPM-PBM model. In: : . Paper presented at 12th International Symposium on Rock Fragmentation by Blasting, Fragblast 12, Luleå, Sweden on June 9-15, 2018.
Open this publication in new window or tab >>Numerical investigation for timing effects on fragmentation based on a coupled FEM-BPM-PBM model
2018 (English)Conference paper, Published paper (Refereed)
National Category
Engineering and Technology Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-69770 (URN)
Conference
12th International Symposium on Rock Fragmentation by Blasting, Fragblast 12, Luleå, Sweden on June 9-15, 2018
Available from: 2018-06-21 Created: 2018-06-21 Last updated: 2018-06-27
Yi, C., Johansson, D. & Nyberg, U. (2018). Numerical modelling on short delay blast-induced fragmentation and vibration. Blasting and Fragmentation, 12(2), 105-116
Open this publication in new window or tab >>Numerical modelling on short delay blast-induced fragmentation and vibration
2018 (English)In: Blasting and Fragmentation, ISSN 1937-6359, Vol. 12, no 2, p. 105-116Article in journal (Refereed) Published
Abstract [en]

Blasting operations can fragment rock mass into smaller pieces and meanwhile induce vibration anddamage in remaining rock mass. A series of small-scale laboratory tests were carried out to investigatethe effects of short delay times on fragmentation. These tests were modeled using a coupledFEM-BPM-PBM model in the LS-DYNA code. In the model, the remaining rock is representedby a finite element model (FEM) and the rock to be blasted is represented by a bonded particlemodel (BPM). The detonation of explosives is described with a particle blast method (PBM). Thefragment size distribution was obtained with a code developed in Perl programming language. Theblast-induced vibration and damage in the remaining rock mass were evaluated. The results showthat the coupled FEM-BPM-PBM model can be employed to evaluate both fragmentation in theblasted domain and the blast-induced damage and vibration in the remaining rock mass.

Place, publisher, year, edition, pages
Cleveland: International Society of Explosives Engineers, 2018
Keywords
blasting, short delay, fragmentation, vibration, numerical modelling
National Category
Geotechnical Engineering
Research subject
Mining and Rock Engineering; Centre - Swedish Blasting Research Centre (SWEBREC)
Identifiers
urn:nbn:se:ltu:diva-73819 (URN)
Note

Validerad;2019;Nivå 1;2019-07-05 (johcin)

Available from: 2019-05-02 Created: 2019-05-02 Last updated: 2019-07-05Bibliographically approved
Danielsson, M., Johansson, D. & Schunnesson, H. (2018). The Influence of Blast Fragmentation on Loadability in Sublevel Caving. In: Kevin Hachmeister (Ed.), Proceedings of the forty-forurth annual conference on explosives and blasting technique: . Paper presented at 44th Annual Conference on Explosives and Blasting Technique, San Antonio, Texas, Jan. 28–31 2018.
Open this publication in new window or tab >>The Influence of Blast Fragmentation on Loadability in Sublevel Caving
2018 (English)In: Proceedings of the forty-forurth annual conference on explosives and blasting technique / [ed] Kevin Hachmeister, 2018Conference paper, Published paper (Refereed)
Abstract [en]

In sublevel caving, blasted material flows gravitationally into the drawpoint from above in a periodical manner. This type of flow behavior entails muck pile conditions that are variable along the course of extraction. The effect of this variability on the LHD (Load-Haul-Dump) operation in terms of loading efficiency and ability to undermine the blasted ring is not fully understood as of today. This paper presents results from a field test in LKABs Malmberget mine in Sweden, where the influence of fragmentation on the loading operation has been studied in detail. Drawpoint filming was conducted for extraction of two rings equivalent of roughly 10000 metric tons (~9842 long tons) of material each. The analysis includes fragmentation measurements, muck pile classification, and general estimations in terms of loadability. Further, an evaluation of LHD machines from two different manufacturers was conducted to identify and highlight differences. The results show that fragmentation, muck pile compactness, and flow characteristics are all interdependent. Flow disturbances and the subsequent loading of compacted fine material in the back of the ring have been identified as the main reason for occurring problems and prolonged digging times. However, the ability to sufficiently undermine the blasted ring has been identified to primarily depend on digging depth which is only observed to be high during flow disturbances. An absence of flow disturbances seem to promote high loading efficiency but simultaneously limit the maximum digging depth. A mid-range particle size distribution with a low amount of fines has proven beneficial for overall loading efficiency. The various LHDs employed showed significant variations in terms of ability to handle difficult loading situations (e.g. compactness, boulders, etc.).

National Category
Other Engineering and Technologies not elsewhere specified Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-70536 (URN)
Conference
44th Annual Conference on Explosives and Blasting Technique, San Antonio, Texas, Jan. 28–31 2018
Available from: 2018-08-22 Created: 2018-08-22 Last updated: 2018-08-28
Johansson, D. & Schunnesson, H. (Eds.). (2018). Twelfth International Symposium on Rock Fragmentation by Blasting: Fragblast 12. Paper presented at Twelfth International Symposium on Rock Fragmentation by Blasting; Luleå,Sweden on June 9-15, 2018. Luleå University of Technology
Open this publication in new window or tab >>Twelfth International Symposium on Rock Fragmentation by Blasting: Fragblast 12
2018 (English)Conference proceedings (editor) (Refereed)
Place, publisher, year, edition, pages
Luleå University of Technology, 2018
National Category
Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-68578 (URN)978-91-7790-134-1 (ISBN)978-91-7790-135-8 (ISBN)
Conference
Twelfth International Symposium on Rock Fragmentation by Blasting; Luleå,Sweden on June 9-15, 2018
Available from: 2018-05-02 Created: 2018-05-02 Last updated: 2019-05-28Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5165-4229

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