Change search
Refine search result
1 - 48 of 48
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Beyglou, Ali
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Target fragmentation for efficient loading and crushing: The Aitik case2017In: The Southern African Journal of Mining and Metallurgy, ISSN 2225-6253, E-ISSN 1543-9518, Vol. 117, no 11, p. 1053-1062Article in journal (Refereed)
    Abstract [en]

    Blast-induced fragmentation has a significant influence on the operational efficiency of open pit mines, especially on loading and crushing, the two immediate tasks after blasting. This study presents an empirical method to determine the target fragmentation for efficient loading and crushing at the Aitik mine in Sweden. In the study, the loading efficiency of rope shovels was correlated to the energy consumption and throughput of a gyratory crusher. Two photographic techniques were utilized to assess the feed fragmentation, considering the lithological origin of the ore as an indicator of hardness. The results indicate ore hardness is most influential in mid-range fragmentation, with a marginal effect in coarser fragmentations. The influence of fragmentation is more pronounced in the coarse region, with a sudden reduction in efficiency for P80 values coarser than 800 mm. The results suggest tailoring the fragmentation to a P80 of 600-800 mm could lead to higher operational efficiency at Aitik. 

  • 2.
    Beyglou, Ali
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Face to Surface –Task 1: Baseline Mapping of the Mining Operation in Aitik2015Report (Other academic)
    Abstract [en]

    “Face to Surface” is a project within the strategic innovation program “Mining and Metals”, which is a collaboration between Vinnova, Formas and Energy Agency of Sweden with additional funding from Boliden Mineral AB and LKAB. The project is aimed to improve productivity and efficiency of mining activities through optimization of the overall production chain. The current status report corresponds to the first task of the project–Baseline Mapping.The report presents the overall process chain of mining operation in Boliden Aitik copper mine, Sweden. The production chain is initially described as a system of singular processes. Each process is then described in more details, including inter-relations and downstream effects of each process within the operation. The report provides a basis for identification of potential fields of improvement in the process. The subsequent tasks of the project will be conducted upon internal discussions based on the findings of this report.

  • 3.
    Beyglou, Ali
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Nils
    Boliden Mineral AB.
    Adjusting Initiation Direction to Domains of Rock Mass Discontinuities in Aitik Open Pit Mine2015In: 11th International Symposium on Rock Fragmentation by Blasting: Fragblast11, Carlton, Vic: The Australasian Institute of Mining and Metallurgy, 2015, p. 385-391Conference paper (Refereed)
    Abstract [en]

    As demand for optimisation of mining processes increases, more attention is drawn to blast performance and fragmentation improvement. Fractures and discontinuities are among the most influential factors in blast results, therefore one of the initial steps towards blast optimisation is to gather information about the rock mass and integrate it in blast design. This paper presents a method for assessment of rock mass discontinuities and integrating it in production blasts in the Aitik open pit copper mine in Sweden. 3D photogrammetric techniques were utilised to map discontinuities and distinguish domains of similar geologic structures in the pit. As a pilot study for a future campaign, four different initiation directions were tested through six pilot blasts in one of the domains. The results were compared in terms of swell and loading efficiency of rope shovels to identify the correlation between blast performance and initiation direction compared to major discontinuity families. It was established that in the trial domain, blasts initiated towards north or north-west yielded larger swell and better performance of loading. Comparing these blasts with discontinuity families show that there is a correlation between blast performance and initiation direction according to the dip and strike of these discontinuities. Such knowledge can be used for future blasts in the same domain to increase long-term operational efficiency through slight modifications in drill pattern and initiation design.

  • 4.
    Danielsson, Markus
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Ghosh, Rajib
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Navarro Miguel, J.
    Universidad Politechnica de Madrid.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Utilizing production data to predict operational disturbances in sublevel caving2017In: Mine Planning and Equipment Selection (MPES 2017): Proceeding of the 26th International Symposium on Mine Planning and Equipment Selection Luleå, Sweden, August 29-31, 2017 / [ed] Behzad Ghodrati, Uday Kumar, Håkan Schunnesson, Luleå: Luleå tekniska universitet, 2017, p. 139-144Conference paper (Refereed)
  • 5.
    Danielsson, Markus
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    The Influence of Blast Fragmentation on Loadability in Sublevel Caving2018In: Proceedings of the forty-forurth annual conference on explosives and blasting technique / [ed] Kevin Hachmeister, 2018Conference 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.).

  • 6.
    Greberg, Jenny
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Project: Face to Surface2014Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Projekt inom ramen för SIO STRIM

  • 7.
    Gustafson, Anna
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Face to Surface: a fragmentation study2016Report (Refereed)
    Abstract [en]

    As ore grades have decreased and the mining depth has increased over the past few decades, other characteristics than ore grade and tonnage are becoming important. The underground mining process, from in-situ rock mass characteristics to the final mill product with fully liberated minerals, consists of a chain of unit operations that impact, and are influenced by, fragmentation. This report presents the baseline mapping of the project “From Face to Surface”, studying the effects of fragmentation on the process flow in an underground SLC mine. It analyses the underground unit operations in detail, from mine planning to shafts, and maps the blast fragmentation’s effect on the process flow. The goal is to provide a deeper understanding of fragmentation´s effect on different unit operations. The objective is to describe the mining operation at Luossavaara-Kiirunavaara AB (LKAB) and identify key areas for improving fragmentation. To understand how fragmentation influences different operations in the mine, the project conducted a literature study, collected data and interviewed mine personnel in LKAB’s Malmberget mine. Data were collected from the mine’s internal systems, such as GIRON, WOLIS, IP21 and a local drilling data system. The interviews were conducted in cooperation with research personnel from the mine.This baseline mapping shows that the mining operation in Malmberget is affected by fragmentation in several ways. For some unit operations, the fragmentation has a large impact, while for others, it has none at all. The influence of fragmentation starts with the loading operation after the initial blasting and ends with the crushing operation. For the former, boulders are the largest problem, as they cause a great deal of idle time, either when they have to be moved to a separate drift for secondary blasting or when they create hang-ups in the ore passes. When boulders are dumped into the ore passes, they risk damaging the ore pass walls. If boulders create a hang-up, it has to be removed. If the hang-up must be removed with explosives, there is a risk of further damaging the ore pass. In addition, the toxic fumes created by the explosives hinder production until the pass is ventilated. Finally, hang-ups affect the transportation operation as the trucks cannot use an ore pass blocked by a hang-up or closed for ventilation of toxic fumes. There is also a slight possibility that a boulder which does not get stuck in the ore pass will get stuck on a truck. The last operation affected by fragmentation is crushing; boulders and large fragments risk creating a hang-up in the crusher. There are no reports of problems related to fragmentation after this point.The results suggest that further work and mine trials are required in the following areas: drilling, loading, ore passes and crushers.

  • 8.
    Gustafson, Anna
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Jonsson, Kristina
    LKAB.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    From Face to Surface: a Fragmentation Study2016In: Seventh International Conference & Exhibition on Mass Mining : (MassMin 2016), Sydney: The Australian Institute of Mining and Metallurgy , 2016, p. 555-562Conference paper (Refereed)
    Abstract [en]

    The underground mining process, from in-situ characteristics of the unmined rock mass to the final mill product with fully liberated minerals, consists of a chain of unit operations. Some of them influence fragmentation while fragmentation impacts others. From a production point of view, fragmentation is a key parameter for the proper functioning of many unit operations and affects total production; it influences the ability to load, haul and crush the rock later in the process. Fragmentation varies because of rock mass strength, the presence of joints, the chosen explosive, specific charge (kg/m3) and quality of drill holes. The efficiency and result of unit operations such as drilling, blasting, loading and crushing depend on the rock properties which vary throughout a mine. Generally speaking, operations are not well adapted to the actual rock properties, leading to a non-optimised flow in production. This paper presents the initial part of a project that will build knowledge on the impact of fragmentation on each step of the production chain in an underground mine. It identifies the key parameters of fragmentation which influence the overall energy consumption and productivity in a mining operation through interviews, mine visits and a literature review. In the subsequent stages of the project, a number of field tests in the case study mine will address important segments of the production process where fragmentation is a major obstacle to improvements. Optimising the entire process, rather than isolated unit operations, will lead to increased productivity, decreased amount of interruptions and lower energy consumption.

     

  • 9.
    Ittner, Henrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Svensk Kärnbränslehantering AB.
    Olsson, Mats
    EDZ Consulting AB.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Multivariate evaluation of blast damage from emulsion explosives in tunnels excavated in crystalline rock2019In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 85, p. 331-339Article in journal (Refereed)
    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.

  • 10.
    Ittner, Henrik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Swedish Nuclear Fuel and Waste Management Company (SKB).
    Åkeson, Urban
    Swedish Transport Administration (TRV).
    Christiansson, Rolf
    Swedish Nuclear Fuel and Waste Management Company (SKB).
    Olsson, Mats
    EDZ Consulting AB.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Recent Swedish Studies on the Extent of Blast Damage after Excavation2016Conference paper (Refereed)
    Abstract [en]

    This paper presents two recent studies on the extent of blast damage after excavation in crystalline rock. The Swedish Transport Administration and the Swedish Nuclear Fuel and Waste Management Company (SKB) are both under regulations to limit excavation damage during construction of tunnels. SKB is also required to limit the Excavation Damage Zone (EDZ), as this could be a potential flow path for radionuclides in the planned repository for spent nuclear fuel.Presented in this paper are investigations of blast damage from three tunnel sites, a road tunnel, an experimental tunnel in Äspö Hard Rock Laboratory and an underground subway depot.As expected the fractures resulting from the bottom charge are both longer and more frequent then those mapped in the column charge. The results show that the requirement to limit blast damage according to Swedish regulations was fulfilled for the column charge at the three studied sites.

  • 11.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effects of confinement and initiation delay on fragmentation and waste rock compaction: Results from small scale tests2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sub-level caving (SLC) is classified as a mass mining method and there is an increasing interest in its application worldwide and in a very wide range of geotechnical environments. Design of sub-level blasting rounds and optimization has become more important now when the sizes of the blasting rings have become larger. Sufficient fragmentation is one of the key factors and in confined blasting, as in sub-level-caving, this influences the mobilization of the blasted ring. The caved rock or debris at the interface first acts as a wave trap i.e. the debris at the SLC interface reduces the fragmentation and the swelling of the blasted ring and it dissipates the explosive energy. These phenomena may immobilize the blasted ring, causing ore losses.Small-scale blasting has been carried out to investigate and clarify this phenomenon. To minimize geometrical and geological effects, tests were made on Ø140 mm cylinders of magnetic mortar, which fractures like magnetite but is a less variable material. The cylinders were placed inside a Ø300 mm steel cylinder and confined by packed aggregate. The explosive source was decoupled PETN cord with different strengths in a center hole, which gave a specific charge between 0.2 and 2.6 kg/m3. The magnetic mortar and the nonmagnetic aggregate allowed for post-blast magnetic separation. The setup provides very repeatable results. The fragmentation of the blasted mortar and the aggregate plus the swelling of the confined mortar cylinders have been measured. As a reference, free mortar cylinders without radial confinement were used. More than 160 tests have been made with the cylindrical set-up.The results show that the confinement results in fragmentation being coarser when compared to that from free cylinders, and that the properties of the debris have a strong influence on the fragmentation and the swelling of the blasted materiel/compaction of the confining material. For the latter, a freezing-slicing method has been developed. The cylinders could thus be sliced perpendicular to the charged hole and then photographed to measure the radial expansion at different heights. The acoustic impedance between blasting material and confining debris has been applied to give a material description in a simple and physical form. This, in combination with the specific charge, has been shown to influence the fragmentation and compaction to a great extent. For the compaction, the porosity of the confining debris is also an influencing factor. Two prediction equations have been presented with high coefficients of determination, both for fragmentation and compaction. The tests have also been shown to be a good input for numerical modelling of blast compaction and reliable input for future numerical modelling of blast fragmentation. Further, 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 and burden were 110 mm 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 to no shock wave interactions. The decrease of x50 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.

  • 12.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Fragmentation and waste rock compaction in small-scale confined blasting2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sub-level caving (SLC) is an important mass mining method, used at LKAB e.g. The caved rock or debris at the SLC interface reduces the fragmentation and the swelling of the blasted ring and it dissipates the explosive energy. These phenomena may immobilize the blasted ring, causing ore losses. There are two major factors that influence the mobilization of the blasted ring, fragmentation and swelling of the blasted material. The caving process is influenced by also the stiffness of the waste rock, which is dependent in some way by the compaction that the blast ring contributes to. To investigate these phenomena in large-scale is very difficult and nearly impossible due to the mining method itself. Therefore model scale tests have been made to understand the mechanisms of rock breakage and therefore fragmentation under relatively confined conditions. To minimize geometrical and geological effects, tests were conducted on Ø140 mm cylinders of magnetic mortar, which fractures like magnetite but is a less variable material. The cylinders were placed inside an Ø300 mm steel or plastic cylinder and confined by packed aggregate. PETN cord with different strengths in a centred hole gave a specific charge between 02 and 2.6 kg/m3. This thesis describes and discusses how fragmentation and compaction, the reverse of swelling, depend on the specific charge for different types of debris confinement. Four different types of debris have been tested and for one of them a confining pressure of about 0.42 or 0.86 MPa was induced by a slotting and bolting of the steel cylinder. The results show both that the passive confinement makes the fragmentation considerably coarser than from free cylinders and that the properties of the debris have a strong influence on both fragmentation and swelling. The effect of the confining pressure was relatively small however and interpreted mainly by changes in debris porosity. The magnetic mortar and the non-magnetic aggregate allow for post-blast magnetic separation. The setup provides extremely repeatable results. The fragmentation of the blasted mortar and the aggregate plus the compaction (reverse swelling) of the confined mortar cylinders have been measured. Free mortar cylinders were used as a reference To date, more than 160 cylinders have been shot and evaluated in terms of fragmentation or compaction. It has been clearly shown that the test set-up is robust and gives repeatable results. The small scale tests are a first step to increase the understanding of confined blasting as in sub-level caving. By using the acoustic impedance between the blasted material and the confining debris, a relationship for both fragmentation and compaction have been found depending on material, specific charge and physical properties of the debris. Regression analysis has been used for both tasks, where the two statistical hypotheses clearly have good agreement with actual data i.e. the prediction models can forecast both the fragmentation and compaction for this set-up with reasonable accuracy The results can be comparable with confined blasting in large scale, this both that it have representative design parameters that fulfil in many ways the scaling laws and the second is that it can be linked to other comparisons between large-scale and small-scale, where the similarities have been shown. The results from this thesis have shown to be a good input for numerical modelling, where confined blasting is one of the new tasks. This will be a part of the coming work to optimally design SLC-rings for maximum output of ore.

  • 13.
    Johansson, Daniel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Stenman, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Håkan, Schunnesson
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Shock front curvature measurements of emulsion explosives2019In: Proceedings of the 10th EFEE / [ed] Roger Holmberg, 2019Conference 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.

  • 14.
    Johansson, Daniel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Ouchterlony, Finn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Fragmentation in small-scale confined blasting2011In: International Journal of Mining and Mineral Engineering, ISSN 1754-890X, E-ISSN 1754-8918, Vol. 3, no 1, p. 72-94Article in journal (Refereed)
    Abstract [en]

    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.

  • 15.
    Johansson, Daniel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Ouchterlony, Finn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Shock wave interactions in rock blasting: the use of short delays to improve fragmentation in model-scale2013In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 46, no 1, p. 1-18Article in journal (Refereed)
    Abstract [en]

    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

  • 16. Johansson, Daniel
    et al.
    Ouchterlony, Finn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edin, J.
    Luleå tekniska universitet.
    Martinsson, L.
    Luleå tekniska universitet.
    Nyberg, Ulf
    Blasting against confinement, fragmentation and compaction in model scale2008In: MassMin 2008: Proceedings of the 5th International Conference and Exhibition on Mass Mining, Lulea, Sweden 9-11 June 2008 / [ed] Håkan Schunnesson; Erling Nordlund, Luleå: Luleå tekniska universitet, 2008, p. 681-690Conference paper (Refereed)
  • 17.
    Johansson, Daniel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Ouchterlony, Finn
    Nyberg, Ulf
    Blasting against aggregate confinement: fragmentation and swelling in model scale2007In: Fourth EFEE World Conference on Explosives and Blasting: [Vienna Conference Proceedings 2007] / [ed] Peter Moser, European Federation of Explosives Engineers , 2007, p. 13-26Conference paper (Refereed)
    Abstract [en]

    Sub-level caving (SLC) is classified as a mass mining method and there is increasing interest in its application world wide and under a very wide range of geotechnical environments. In terms of flow, the caved rock or debris at the interface first acts as a wave trap, which may reduce the fragmentation. Model scale tests are being made to understand the mechanisms of rock breakage and therefore fragmentation under relatively confined conditions. To minimize geometrical and geological effects, tests were conducted mainly on cylinders of magnetic mortar of size Ø140×280 mm and PETN cord with different strengths was used as explosive in a center hole, giving a specific charge between 0,2 and 2,6 kg/m3. The size distributions of the blasted material and the aggregate as well as the swelling of the cylinders have been measured. For the latter, a freezing-slicing method was developed. The results show that the confinement results in fragmentation being coarser when compared to that from free cylinders, and that the properties of the debris have a strong influence on the fragmentation and the swelling.

  • 18. Johansson, Daniel
    et al.
    Ouchterlony, Finn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Modellförsök med sprängning mot rasmassor: inverkan på styckefall och svällning2007In: Bergsprängningskommittén : diskussionsmöte BK 2007: protokoll från Bergsprängningskommitténs diskussionsmöte i Stockholm den 13 mars 2007, 2007, p. 105-120Conference paper (Other academic)
  • 19.
    Johansson, Daniel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, HåkanLuleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Twelfth International Symposium on Rock Fragmentation by Blasting: Fragblast 122018Conference proceedings (editor) (Refereed)
  • 20.
    Johansson, Daniel
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Villegas, Tomas
    Ouchterlony, Finn
    Dynamic blast compaction of some granular materials: small-scale tests and numerical modelling of a mining-related problem2010In: International Journal of Mining and Mineral Engineering, ISSN 1754-890X, E-ISSN 1754-8918, Vol. 2, no 2, p. 79-100Article in journal (Refereed)
    Abstract [en]

    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.

  • 21.
    Navarro, Juan
    et al.
    Universidad Politécnica de Madrid – E.T.S.I. Minas y Energía, Madrid, Spain.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Ghosh, Rajib
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Segarra, Pablo
    Universidad Politécnica de Madrid – E.T.S.I. Minas y Energía, Madrid, Spain.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Sanchidrián, José Ángel
    Universidad Politécnica de Madrid – E.T.S.I. Minas y Energía, Madrid, Spain.
    Application of drill-monitoring for chargeability assessment in sublevel caving2019In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 119, p. 180-192Article in journal (Refereed)
    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.

  • 22.
    Parida, Aditya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edelman, Martin
    Success of reliability centered maintenance (RCM) lies in its implementation: a case study2004In: Euromaintenance 2004: Libro de conferencias, Conference Proceedings : 17° Congreso Europeo de Mantenimiento, 17th European Maintenance Congress : 11th - 13th of May, 2004 Barcelona - Spain, Barcelona: Asociacion Espanola de Mantenimiento , 2004, p. 229-236Conference paper (Refereed)
  • 23.
    Petropoulos, N.
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Wimmer, Matthias
    LKAB, Kiruna.
    Johansson, D.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, E.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Compaction of confining materials in pillar blast tests2018In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 51, no 6, p. 1907-1919Article in journal (Refereed)
    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.

  • 24.
    Petropoulos, Nikolaos
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Beyglou, Ali
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Novikov, Evgeny
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Improved blasting performance through precise initiation2013In: EFEE-7th World Conference on Explosives & Blasting, Moscow: European Federation of Explosives Engineers , 2013, Vol. 1, p. 20-26Conference paper (Refereed)
    Abstract [en]

    Blast-induced fragmentation is an important factor in optimization of downstream processes in a mine. Several researchers believe that the fragmentation can be improved by means of precise short inter-hole delay times. Six full-scale trials with different inter-hole delay times of 1, 3, 6 and 42 ms (0.14, 0.42, 0.84 and 6 ms/m of burden, respectively) were conducted in Boliden Aitik open pit copper mine in Sweden. Electronic detonators were used for short inter-hole delay times, which correspond to different wave interactions between the neighboring blast holes. All the trials were carried out in more or less similar geological conditions. MWD data, swelling, fragmentation and crusher efficiency have been evaluated in the trials. Based on these trials, the short inter-hole delay times did not have a significant effect on fragmentation, swelling and crushability. However, a reduced number of boulders was observed for short delays, suggesting that the coarse region of the distribution curve was influenced rather than the fine part of it.

  • 25.
    Petropoulos, Nikolaos
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Beyglou, Ali
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Novikov, Evgeny
    Boliden Mineral AB.
    Fragmentation by blasting through precise initiation: Full scale trials at the Aitik Copper mine2014In: Blasting and Fragmentation, ISSN 1937-6359, Vol. 8, no 2, p. 87-100Article in journal (Refereed)
    Abstract [en]

    Fragmentation is an important factor for improving downstream processes in mine operations. Six trials have been conducted at the Aitik copper mine to investigate the effect of ultra-short inter-hole delay times, i.e. smaller than 1 ms/m of burden, on fragmentation. Swelling, MWD data and crusher efficiency were also evaluated for trials. According to the results, the effect of examined short inter-hole delay times, i.e. 0.14 to 0.86 ms/m of burden, on fragmentation was found to be marginal. Delay time of 0.43 ms/m of burden resulted in slightly finer fragmentation and larger swell; however, the effect of short delays was overshadowed by the effect of small variations in specific charge.

  • 26.
    Petropoulos, Nikolaos
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Crushed aggregate response upon impact in dry and wet conditions2017In: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 7, no 3, p. 1-22Article in journal (Refereed)
    Abstract [en]

    This paper presents results from a series of impact tests upon coarse-grained crushed aggregate. The material has been evaluated for two conditions, i.e. dry and wet (pendular state). Three main sets of test configurations were used with respect to compactive effort (low, medium and high) which was defined by the impact velocity of a drop hammer. Three accelerometers were installed in an impact machine to measure deceleration of the drop hammer and accelerations in the tested material at three different locations. The studied parameters were density, compaction, angle of repose, critical angle and particle size distribution. The results showed that the wet material gives larger density as well as critical angle. However, there was no discernible change in particle size distribution.

  • 27.
    Petropoulos, Nikolaos
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Novikov, Evgeny
    Beyglou, Ali
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Improved blasting results through precise initiation: results from field trials at the Aitik open pit mine2013Report (Refereed)
    Abstract [en]

    Blast-induced fragmentation plays a leading role on mining efficiency, hence many studies have been conducted in order to understand the mechanisms behind rock breakage and to improve the fragmentation. This report presents the results from field tests conducted at the Aitik mine belonging to Boliden Mineral AB in Sweden, which is part of a project called Vinnova. The project aims to evaluate the effects of short delay time blasting on fragmentation and other post-blast parameters which influence the comminution process, e.g. swelling and crushing.A total number of 6 benches were assigned for trials with different inter-hole delay times. Two of the benches were blasted with pyrotechnic Nonel caps and were used as references for further comparisons. Two benches were blasted with 1 ms of inter-hole delay time by use of electronic detonators. Two other benches were also blasted by electronic detonators, but with 3 ms and 6 ms of inter-hole delay time respectively. MWD (Measure While Drilling) system was used to log and analyze the drilling process in order to investigate the penetration rate and specific energy of drilling, which represent the hardness of the rock. GPS (Global Positioning System) and RTK (Real time Kinematic System) were used for measurements of benches’ swelling. The blasts were also filmed using a high-speed camera. Image analysis with Split-Desktop software was used to analyze the fragmentation of the rock after blasts. A series of images was shot from trucks carrying the ore and was later analyzed to obtain the fragmentation for each bench. Minestar integrated operation and mobile equipment management system was used to log the data from the fleet in the mine. The data were later used together with the crusher energy consumption logs to evaluate the energy efficiency of the crushing process for the ore from each bench.The tests showed that the inter-hole delay time of 3 ms resulted in the finest fragmentation among all benches; all examined values i.e. x50, x80 and xmax showed improvements upon other benches. However, the crushing energy of the ore from this trial was the highest among all. Two trials with 1 ms inter-hole delay time did not result in any significant variation compared to reference benches. The difference in x50 values were ignorable, the same is true for crushing energy of the mentioned trials. The bench with inter-hole delay time of 6 ms resulted in the lowest crushing energy among other trials. However, the bench gave more boulders and coarser fragmentation compared to reference benches.Altogether, the results did not lead to any solid conclusion regarding the effect of the short delay times on fragmentation. Such ambiguity might be resulted by various sources of errors in data acquisition and analysis, as well as uncertainties regarding geology of the test area. In order to investigate the effect of delay times on blast results, more trials with more detailed data acquisition method is necessary.

  • 28.
    Petropoulos, Nikolaos
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Ouchterlony, Finn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Fragmentation under different confinement conditions and the burden behaviour: small scale tests2012In: Measurement and Analysis of Blast Fragmentation: Workshop Hosted by FRAGBLAST 10 - The 10th International Symposium on Rock Fragmentation by Blasting / [ed] Jose A. Sanchidrian Blanco; Ashok Kumar Singh, Boca Raton, Fla.: CRC Press/Balkema , 2012, p. 61-70Conference paper (Refereed)
    Abstract [en]

    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.

  • 29.
    Petropoulos, Nikolaos
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mihaylov, Dimitar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    A Suggested Method for the Study of Crushed Aggregate Response to Dynamic Compaction2017In: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 22, no 02, p. 387-406Article in journal (Refereed)
    Abstract [en]

    Soil improvement by dynamic compaction has been extensively used all around the world in large civil engineering projects. Limited number of laboratory tests has been conducted to study the behavior of soil material under dynamic loading. A suggested method is presented in this paper which includes a new laboratory apparatus and experimental procedure as well as data analysis. The suggested impact machine is a drop hammer type machine, it can host up to 37.5 mm particle size in a coarse-grained aggregate matrix independent of its conditions, i.e. saturated or unsaturated, it is also flexible in terms of weight and size of the drop hammer and the mold. The machine is equipped with accelerometers for continuous monitoring of the sample’s behavior during impact. The experimental procedure shows the steps for conducting consistent dynamic compaction tests. It also describes how the measurements should be conducted. These measured quantities correspond to key parameters such as density, angle of repose and compaction. Finally, a case example demonstrates the function of the machine and the analysis of the recorded data.

  • 30.
    Petropoulos, Nikolaos
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mihaylov, Dimitar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Wimmer, Matthias
    Nordqvist, Anders
    Mining Technology R and D, LKAB Kiruna Mine.
    Design of equipment for dynamic burden measurements2015In: 11th International Symposium on Rock Fragmentation by Blasting: FragBlast11, Carlton VIC: The Australasian Institute of Mining and Metallurgy, 2015, p. 493-500Conference paper (Refereed)
    Abstract [en]

    The flowability of the caved rock masses in the sublevel caving (SLC) mining method is of greatimportance. During the blasting process of a SLC-ring, the caved rock mass in front of the ring iscompacted. As a result of this compaction, the mechanical properties of the fractured rock masseschange, for example void ratio, angle of internal friction and structure of the compacted material.The changed mechanical properties of caved rock mass and recent blasted material can influencethe mobility of the material, which could result in blockage of the flow path of the material.The identification of the involved mechanisms in this process can be done after a series of testsin different scales. However, there is no available equipment for dynamic measurements duringblasting, ie velocity and displacement of the burden and in the caved masses. This study focuses onthe development and laboratory evaluation of a measuring system that can be installed in a borehole.The first trial was carried out in a pillar, where two blastholes had been drilled (9.5 m) parallel withthe drift and two measuring holes (16.5 m) were perpendicular to the drift. Two measuring systemswere installed in the measuring holes. Some preliminary tests were carried out to find suitableinitiation procedures for the emulsion explosive. Applicability and robustness of the developedmeasuring system were also evaluated. In addition to these tests, an expandable cement mixture wasdeveloped to firmly anchor the measuring systems in the boreholes. The measuring system consistsof an anchor, armoured cable in a pulling tube and a protective case. The anchor is equipped withuniaxial and triaxial accelerometers. A potentiometric measuring system for displacement up to 2 mis installed at the end of the pulling tube and connected to an extendable spiral cable. All sensorsare connected to a data acquisition system (DAS). Both measuring systems have their own DAS toacquire data in case of failure of one of the systems. The measuring system was tested in laboratoryconditions with impact velocity up to 10 m/s. It was proven to be functional and gave reliable results.

  • 31.
    Sjöberg, Jonny
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schill, Mikael
    DYNAmore Nordic AB, Linköping.
    Hilding, Daniel
    DYNAmore Nordic AB, Linköping.
    Yi, Changping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Computer simulations of blasting with precise initiation2012Conference paper (Refereed)
    Abstract [en]

    Using blasting caps with electronic delay units, it has become possible to employ wave superposition in rock blasting. This paper presents computer simulations to investigate the hypothesis that fragmentation is improved in areas between blast holes where the tensile waves meet, overlap and interact. In this study, a numerical methodology using the code LS-DYNA was developed. LS-DYNA is a commercially available multi-purpose finite-element code, which is well suited to various types of dynamic modeling. Two different element formulations were used — Euler formulation in, and close to, the blast hole, and Lagrange formulation in the rock volume farther from the blast hole. The models used have a resolution (element size) of 50 mm and comprise approximately 20 million elements. Single and dual blast hole configurations have been studied, and a methodology to calculate possible fragmentation based on model interpretation was developed. The results showed that the amount of explosives and the blast hole spacing had the largest effect on fragmentation. The effect of varying delay times was small and local, implying that a significant increase in fragmentation should not be expected through wave superposition.

  • 32.
    van Eldert, Jeroen
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Ittner, Henrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Evaluation of Alternative Techniques for Excavation Damage Characterization2016In: ITA-AITES World Tunnel Congress 2016, WTC 2016 / [ed] Society for Mining, Metallurgy & Exploration (SME), United States of America, 2016, Vol. 2, p. 1168-1177Conference paper (Refereed)
    Abstract [en]

    Numerous aspects of underground construction, from structural stability to construction costs, depended on the tunnel quality, including blast damage and the Excavation Damage Zone. Accurately quantifying the extent and severity of damaged rock is a problem. Recent technical developments in the field of Measurement While Drilling (MWD), including software for on-board logging and on-site analysis, have shown potential for rock-mass characterization. Ground Penetrating Radar (GPR) and P-wave velocity measurement have also improved and show similar potential. This paper explores the use of MWD, GPR and P-wave velocity measurements and uses them in techniques for excavation damage characterization and prediction. The paper is based on data collected from a small underground wastecollection site in central Stockholm, Sweden. The data is correlated against rock-mass characteristics and their responses are evaluated. Results indicate potential for excavation damage characterization for all tested techniques, which could minimize blasting damage and improve the over-all tunnel quality.

  • 33.
    van Eldert, Jeroen
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    The History and Future of Rock Mass Characterisation by Drilling in Drifting: From sledgehammer to PC-tablet2017In: Mine Planning and Equipment Selection (MPES 2017): Proceeding of the 26th International Symposium on Mine Planning and Equipment Selection Luleå, Sweden, August 29-31, 2017 / [ed] Behzad Ghodrati, Uday Kumar, Håkan Schunnesson, Luleå: Luleå tekniska universitet, 2017, p. 99-106Conference paper (Refereed)
    Abstract [en]

    In underground construction projects problematic rock mass conditions are one of the major issues causing cost overruns during the excavation phase. Before a tunneling project starts the rock mass is roughly characterized by a pre-investigation. However, in many cases, these pre-investigation does not portray the rock mass characteristics accurately and do not predict local anomalies in the subsurface. Therefore there is a need for new rock mass characterization methods that can reduce uncertainties and improve the overall tunneling process.

    In the end of the 1880s, rock mass characterization based on manual drill data was investigated and rock masses were quantified using drillability. Since then, the technology has significantly changed with the introduction of hydraulic rock drills, computerized drill rigs, and advanced rock mass classification systems based on drill parameters. Nowadays, automatic drill logging systems and drilling data processing software packages are widely available and commonly used in Scandinavian tunneling projects.

    This technology uses drilling parameters to characterize the rock mass. However, monitored drill parameters are influenced not only by the variations in the properties of the penetrated rock mass but also by the operator and the rig control system that continuously control the applied forces to optimize drilling and prevent jamming. In order to be useful for geomechanical purposes, the drilling data needs to be filtered, normalized and analyzed to refine the rock related response from responses caused by other influencing factors. If successful the data might be used to determine hardness, fracturing and water indicators.

    Even though the technology has shown high potential in laboratory tests and field trials, it is not an obvious choice for all tunneling projects. In this paper, the background of the technology are described and the potential for the future outlined, concluding that the technique probably will be used more extensively in the future. 

  • 34.
    van Eldert, Jeroen
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Schunnesson, Håkan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Saiang, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Application of Measurement While Drilling Technology to Predict Rock Mass Quality and Rock Support for Tunnelling2019In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453XArticle in journal (Refereed)
    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.

  • 35.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Discrete Element Modelling of Blast Fragmentation of a Mortar Cylinder2015Conference paper (Refereed)
    Abstract [en]

    Blasting techniques are widely used to fragment rock masses into smaller pieces. Numerical modelling is an efficient method employed by many researchers in the blasting field. It is difficult for a conventional continuum-based approach such as the finite element method (FEM) to model the rock fragmentation by blasting and the expansion work on the rock by explosive and its detonation products. In this paper, the particle blast method (PBM) was employed to model the behaviour of the detonation and a bonded particle model (BPM) was used to model the brittle material to be blasted. A mortar cylinder with a centrally placed hole for the explosive was modelled and the results were compared to the experimental data. The blast process from crack initiation to fragment formation was analysed. The influence of coupling ratio on fragmentation was also investigated.

  • 36.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Swedish Blasting Research Centre, Luleå University of Technology, Sweden.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Swedish Blasting Research Centre, Luleå University of Technology, Sweden.
    Greberg, Jenny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effects of in-situ stresses on the fracturing of rock by blasting2018In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 104, p. 321-330Article in journal (Refereed)
    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.

  • 37.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Swedish Blasting Research Centre, Luleå University of Technology, Sweden.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Swedish Blasting Research Centre, Luleå University of Technology, Sweden.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Swedish Blasting Research Centre, Luleå University of Technology, Sweden.
    Numerical investigation for timing effects on fragmentation based on a coupled FEM-BPM-PBM model2018Conference paper (Refereed)
  • 38.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical modelling on short delay blast-induced fragmentation and vibration2018In: Blasting and Fragmentation, ISSN 1937-6359, Vol. 12, no 2, p. 105-116Article in journal (Refereed)
    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.

  • 39.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Scattering of SH-waves by a shallow circular lined tunnel with an imperfect interface2016In: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction / [ed] E. Nordlund, T.H. Jones and A. Eitzenberger (eds), 2016Conference paper (Refereed)
    Abstract [en]

    The analytic solutions for the dynamic response of a shallow circular lined tunnel with an imperfectly bonded interface subjected to plane SH-waves are presented in the paper. Complex variable method was used and the imperfect interface was modelled with a linear spring model. The case that the rock is harder than the liner was investigated. The effects of the contact stiffness of the interface, the incident angle, the frequency of the incident wave and the depth of the tunnel were investigated. The results indicate when the frequency of incident waves is low, the variation of contact stiffness of the imperfect interface has a slight effect on the distribution of dynamic stress concentration factor (DSCF) in the rock mass but there is a significant effect on the distribution of DSCF in the liner. When the frequency of incident waves is high, the distribution of DSCF is complicated in the rock mass and in the liner. The variation of the depth of tunnel leads to the cyclical variation of DSCF. The incident angle significantly affects the distribution and value of DSCF. The phenomenon of resonance scattering can be observed when the bond of the interface is extremely weak

  • 40.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Beyglou, Ali
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Stress wave interaction between two adjacent blast holes2016In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 49, no 5, p. 1803-1812Article in journal (Refereed)
    Abstract [en]

    Rock fragmentation by blasting is determined by the level and state of stress in the rock mass subjected to blasting. With the application of electronic detonators, some researchers stated that it is possible to achieve improved fragmentation through stress wave superposition with very short delay times. This hypothesis was studied through theoretical analysis in the paper. First, the stress in rock mass induced by a single-hole shot was analyzed with the assumptions of infinite velocity of detonation and infinite charge length. Based on the stress analysis of a single-hole shot, the stress history and tensile stress distribution between two adjacent holes were presented for cases of simultaneous initiation and 1 ms delayed initiation via stress superposition. The results indicated that the stress wave interaction is local around the collision point. Then, the tensile stress distribution at the extended line of two adjacent blast holes was analyzed for a case of 2 ms delay. The analytical results showed that the tensile stress on the extended line increases due to the stress wave superposition under the assumption that the influence of neighboring blast hole on the stress wave propagation can be neglected. However, the numerical results indicated that this assumption is unreasonable and yields contrary results. The feasibility of improving fragmentation via stress wave interaction with precise initiation was also discussed. The analysis in this paper does not support that the interaction of stress waves improves the fragmentation.

  • 41.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Sjöberg, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical simulation for the influence of delay time on the rock fragmentation2013In: Rock Fragmentation by Blasting, FRAGBLAST 10: Proceedings of the 10th International Symposium on Rock Fragmentation by Blasting / [ed] Pradeep K. Singh; Amalendu Sinha, Boca Raton, Fla.: CRC Press/Balkema , 2013, p. 213-220Conference paper (Refereed)
    Abstract [en]

    With the application of electronic detonators and with short delay times, it may be possible to achieve improved fragmentation through stress wave superposition. This hypothesis was studied through a series of small scale laboratory tests. The results from these tests have subsequently been modeled using the numerical FEM code LS-DYNA and the RHT (Riedel-Hiermaier-Thoma) material model, applying a newly developed methodology for three-dimensional computer simulation of blasting. This work also involved simulating initial damage to the rock through previous blasting, and analyzing the resulting effects. The effect of different delay times showed that through a properly chosen delay time, improved fragmentation could be inferred. Moreover, the initial damage (from the previous row) clearly affected the fragmentation; however, the results indicated that longer delay times (in which the stress wave would have passed the boreholes) also resulted in improved fragmentation, implying that stress wave superposition may not be the primary factor governing fragmentation

  • 42.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Lu, Wenbo
    Rock Mechanics in Hydraulic Structural Engineering, Ministry of Education.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effect of imperfect interface on the dynamic response of a circular lined tunnel impacted by plane P-waves2016In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 51, p. 68-74Article in journal (Refereed)
    Abstract [en]

    A theoretical method for studying the dynamic response of a circular lined tunnel with an imperfectly bonded interface subjected to plane P-waves is presented in the paper. The wave function expansion method was used and the imperfect interface was modeled with a spring model. Two cases were discussed in the paper. In the first case rock is harder than the lining and vice-versa in the second case. The results indicated that the variation in the stiffness of the interface has much influence on the distribution of dynamic stress concentration factors (DSCF) in the rock and the lining. The imperfection of the interface has a more noticeable influence on the DSCF in the rock mass and the lining at high frequency incident wave's scenario than low frequency incident wave's scenario. The resonance scattering phenomena can be observed when the bond is extremely weak. Limiting cases were considered and a good agreement with the solutions available in the literature was obtained.

  • 43.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Swedish Blasting Research Centre, Luleå University of Technology, Sweden.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Swedish Blasting Research Centre, Luleå University of Technology, Sweden.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Swedish Blasting Research Centre, Luleå University of Technology, Sweden.
    Calibration and Validation of Reactive Flow Model Parameters for an emulsion explosive2018Conference paper (Refereed)
  • 44.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Parameter Determination of an Ignition and Growth Model from Emulsion Explosive Tests2015In: 11th International Symposium on Rock Fragmentation by Blasting: FragBlast11, Carlton VIC: The Australasian Institute of Mining and Metallurgy, 2015, p. 585-589Conference paper (Refereed)
    Abstract [en]

    Emulsion explosives are a common industrial explosive and have a non-ideal detonation behaviour. The detonation performance for a given product changes with the charge diameter, ground conditions, confinement and density. The burning process of an emulsion explosive has been modelled with an ignition and growth model in the LS-DYNA code. The parameters in the burning rate function are calibrated by the detonation velocities and the detonation front curvature radii from emulsion explosive tests. A Perl program was developed for an efficient estimation of the parameters, and the results show that the calibrated parameters can predict both detonation velocities and the detonation front curvatures.

  • 45.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Sjöberg, Jonny
    Itasca Consultants AB.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical modelling for blast-induced fragmentation in sublevel caving mines2017In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 68, p. 167-173Article in journal (Refereed)
    Abstract [en]

    The flow behavior of the ore and waste significantly affect the dilution in sublevel caving (SLC) mines. Drill and blast issues are identified as having a substantial impact upon SLC material flow. In the paper, blast-induced fragmentation in SLC was numerically investigated using the LS-DYNA code. A method was presented to evaluate fragmentation based on the damage description and a fragment identification routine implemented in the LS-PREPOST (a pre- and post-processing tool of LS-DYNA). The effects of the delay time and the primer position on fragmentation were investigated. The results indicated that a long delay time gives a finer fragmentation for the cases discussed in the paper. The results also showed that the middle primer and the top primer in SLC can give a fine fragmentation. The limitations of numerical modelling were also discussed.

  • 46.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Sjöberg, Jonny
    Itasca Consultants AB.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Petropoulos, Nikolaos
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    A numerical study of the impact of short delays on rock fragmentation2017In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 100, p. 250-254Article in journal (Refereed)
  • 47.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dynamic analysis for a circular lined tunnel with an imperfectly bonded interface impacted by plane SH-waves2014Conference paper (Refereed)
  • 48.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dynamic response of a circular lined tunnel with an imperfect interface subjected to cylindrical P-waves2014In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 44, p. 165-171Article in journal (Refereed)
    Abstract [en]

    The analytic solutions for the dynamic response of a circular lined tunnel with an imperfect interface subjected to a cylindrical P-wave were presented in the paper. The wave function expansion method was used and the imperfect interface was modeled with a spring model. The interface separating the liner from the surrounding rock was considered to be homogeneous imperfect. The dynamic stress concentration factors (DSCF) of the rock and liner were evaluated and discussed. The effects of incident wave’s frequency, bonding conditions and distance between the wave source and the tunnel were examined. The results showed that the low-frequency incident wave leads to a higher DSCF than the high-frequency incident wave. The bonding conditions have a great effect on the dynamic response of the lined tunnel. When the bond is extremely weak, the resonance scattering phenomenon can be observed. When the distance between the wave source and the tunnel, depending on frequency of the incident wave, is considered as large, the cylindrical wave can be treated as a plane wave. Limiting cases were considered and good agreement with the solutions available in the literature was obtained.

1 - 48 of 48
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf