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van Eldert, J., Schunnesson, H., Johansson, D. & Saiang, D. (2020). Application of Measurement While Drilling Technology to Predict Rock Mass Quality and Rock Support for Tunnelling. Rock Mechanics and Rock Engineering, 53(3), 1349-1358
Open this publication in new window or tab >>Application of Measurement While Drilling Technology to Predict Rock Mass Quality and Rock Support for Tunnelling
2020 (English)In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 53, no 3, p. 1349-1358Article in journal (Refereed) Published
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, 2020
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)000489294700001 ()
Funder
Rock Engineering Research Foundation (BeFo), 344
Note

Validerad;2020;Nivå 2;2020-04-21 (johcin)

Available from: 2019-10-14 Created: 2019-10-14 Last updated: 2020-04-21Bibliographically approved
Manzoor, S., Liaghat, S., Gustafson, A., Johansson, D. & Schunnesson, H. (2020). Establishing relationships between structural data from close-range terrestrial digital photogrammetry and measurement while drilling data. Engineering Geology, 267, Article ID 105480.
Open this publication in new window or tab >>Establishing relationships between structural data from close-range terrestrial digital photogrammetry and measurement while drilling data
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2020 (English)In: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917, Vol. 267, article id 105480Article in journal (Refereed) Published
Abstract [en]

Geologists, mine planners, geotechnical, and mining engineers always strive for maximum information to get a better insight of the rock mass before interacting with it. Over the recent decades, close-range terrestrial digital photogrammetry (CRTDP) has been increasingly used for data acquisition and to support the conventional methods for rock mass characterization. It provides a safe, time-saving and contact-free way to gather enough data to minimize user dependent biases. However, it requires an expensive camera, fieldwork and some software to extract the information from images. In addition, it can over-estimate the rock fracturing sometimes due to weathering of the rock face or poor blasting practices. Measurement while drilling (MWD) data include the responses of different drilling parameters to the variations in the rock mass. MWD data are produced in large quantity, as they come from every hole drilled. These data correspond to the inside variations of rock rather than the surface ones counted in photogrammetry.

In this paper, structural data are obtained from different bench faces of an open pit mine using a commercial software package, ShapeMetriX3D (by 3GSM). These data are compared to the MWD data of the boreholes that were blasted to produce these bench faces to establish certain relationships between drilling parameters and rock mass structures. Half casts of the boreholes with MWD data were visible on the bench faces of the pre-split wall that allowed a better correlation. The results show abrupt changes in MWD parameters for open joints or cavities with some infilling material and overall increases or decreases in parameters for closely spaced bedding planes, fractures or foliations. The results are promising and suggest the method can be used to characterize the rock mass, modify the charging of explosives in blasting operations and facilitate the geological modeling of the rock mass.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
close-range terrestrial digital photogrammetry, measurement while drilling data
National Category
Geotechnical Engineering Mineral and Mine Engineering Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-77788 (URN)10.1016/j.enggeo.2020.105480 (DOI)000518868200021 ()2-s2.0-85077774640 (Scopus ID)
Funder
Vinnova
Note

Validerad;2020;Nivå 2;2020-02-21 (johcin)

Available from: 2020-02-20 Created: 2020-02-20 Last updated: 2020-05-14Bibliographically approved
Yi, C., Nyberg, U., Johansson, D. & Schunnesson, H. (2020). Ignition and Growth Reactive Flow Model for Aluminized Emulsion Explosive. In: : . Paper presented at 46th Annual Conference on Explosives and Blasting Technique.
Open this publication in new window or tab >>Ignition and Growth Reactive Flow Model for Aluminized Emulsion Explosive
2020 (English)Conference paper, Published paper (Refereed)
Abstract [en]

To investigate the non-ideal detonation properties of aluminized emulsion explosive, a series of tests for an emulsion explosive with 5% aluminum powder additive were carried out with mortar confinement. The velocity of detonation (VoD) and the curvature of the detonation front for different charge diameters were obtained from the tests with a high-speed camera. The burning process of the aluminized emulsion explosive has been modelled with the ignition and growth (I&G) flow model in the LS-DYNA code. A routine based on the optimization program LS-OPT code was developed to identify the parameters in the burning rate function with the detonation velocities and the front curvature radii from two tests. A Perl code was implemented in the routine and was used to calculate the VoD, fit the detonation front and obtain the detonation front curvature radii.  The calibrated parameters were used to predict the VoDs and the detonation front curvature radii for the rest cases. The results indicate that both the VoDs and the detonation front curvature radii from the numerical modelling are in good agreement with the experimental results. The numerical results also indicate that the variety of the burn fraction and the peak pressure with the change of charge diameters is reasonable with the calibrated parameters.

National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:ltu:diva-77624 (URN)
Conference
46th Annual Conference on Explosives and Blasting Technique
Available from: 2020-02-03 Created: 2020-02-03 Last updated: 2020-03-11
Schunnesson, H., Shekhar, G., Gustafson, A. & Johansson, D. (2019). A review of mining practices for surface support: an international survey. In: : . Paper presented at Ground Support 2019 (pp. 283-293). Sudbury, Canada
Open this publication in new window or tab >>A review of mining practices for surface support: an international survey
2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This paper reviews mining practices for surface support and identifies four key areas that need attention. An international survey was conducted as part of the Mining Initiative on Ground Support Systems and Equipment III project from 2017 to 2018. The survey used a standardised, web-based questionnaire adapted for personal computers and smartphones. The survey was distributed globally, with data collected from 58 underground mines with different mining conditions and challenges. The results highlight the challenges with regard to safety and automation of surface support for different rock conditions and the advantages and disadvantages of various machines (face drills versus mechanised dedicated bolters versus semi-mechanised bolters) used to install surface support. The survey also shows the ambiguity in the mining community with regard to productivity of mine support. This paper presents an approach for collecting technical data through an online tool, which is inexpensive and effective.

Place, publisher, year, edition, pages
Sudbury, Canada: , 2019
Keywords
surface support, mesh/screen installation, productivity, qualitative review, mine automation
National Category
Engineering and Technology Geotechnical Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-76799 (URN)978-0-9876389-4-6 (ISBN)
Conference
Ground Support 2019
Available from: 2019-11-21 Created: 2019-11-21 Last updated: 2020-04-29
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
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., Johansson, D., Schunnesson, H. & Åhlin, H. (2019). Numerical study of the impact of joints on rock fragmentation by blasting. In: : . Paper presented at EFEE 10th World Conference on Explosives and Blasting.
Open this publication in new window or tab >>Numerical study of the impact of joints on rock fragmentation by blasting
2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Rock masses consist essentially of intact rock and discontinuities such as joints. Blasting is mostly used method for the rock excavation. To investigate the effects of joints on the fragmentation by blasting, three models with different joint patterns and one model without joint were created in the LS-DYNA code. In these models, a bonded particle model was used to represent the rock to be blasted, a finite element model was adopted to model the remaining rock mass and a particle blast model was employed to describe the detonation of explosives. To validate the contact model for joints, the fragmentation pattern and the individual particle motion from two single borehole shot models with and without joints were compared. The numerical results indicated that the existence of joints has a significant effect on fragmentation and vibration. The models with joints produced finer fragmentation compared to the model without joints in the paper. 

Keywords
blasting, joints, fragmentation
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:ltu:diva-76089 (URN)978-0-9550290-6-6 (ISBN)
Conference
EFEE 10th World Conference on Explosives and Blasting
Available from: 2019-09-23 Created: 2019-09-23 Last updated: 2019-12-17
Johansson, D., Nyberg, U., Stenman, U. & Schunnesson, H. (2019). Shock front curvature measurements of emulsion explosives. In: Roger Holmberg (Ed.), Proceedings of the 10th EFEE: . Paper presented at Helsinki Conference Proceedings 2019.
Open this publication in new window or tab >>Shock front curvature measurements of emulsion explosives
2019 (English)In: Proceedings of the 10th EFEE / [ed] Roger Holmberg, 2019Conference paper, Published paper (Refereed)
Abstract [en]

This paper will discuss a suggested methodology and data collection carried out within the EU-project SLIM    (Sustainable Low Impact solution for exploitation of small Mineral deposits based on advanced rock blasting and environmental technologies). The field work took place during 2017 at a test site near Stockholm, Sweden. This paper suggest a method measure the detonation front curvature and the velocity of detonation of explosives. The purpose for this is to increase the understanding of the detonation properties of emulsion explosives as used in many blasting operations around the world. In this study, the key parameters of the performance of the emulsion explosive are its non-ideal detonation front curvature and its velocity of detonation (VOD). The charge diameters have been varied Ø25mm up to Ø65 mm i.e. from nearly critical diameters for a steady detonation up to diameters used in mining/quarrying and tunneling. The suggested methodology also introduce a heavy and thick walled mortar as a confiner for the explosive. This to simulate similar conditions as in blasting in rock. Additional to the proposed methodology and set-up, a scheme to analyze and evaluate the measurements is also proposed.

National Category
Mineral and Mine Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-76528 (URN)978-0-9550290-6-6 (ISBN)
Conference
Helsinki Conference Proceedings 2019
Available from: 2019-10-28 Created: 2019-10-28 Last updated: 2019-11-27
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
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5165-4229

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