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  • 1.
    Petropoulos, N.
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Wimmer, Matthias
    LKAB, Kiruna.
    Johansson, D.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, E.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Compaction of confining materials in pillar blast tests2018Ingår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 51, nr 6, s. 1907-1919Artikel i tidskrift (Refereegranskat)
    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.

  • 2.
    Yi, Changping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Sjöberg, Jonny
    Itasca Consultants AB.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Petropoulos, Nikolaos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    A numerical study of the impact of short delays on rock fragmentation2017Ingår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 100, s. 250-254Artikel i tidskrift (Refereegranskat)
  • 3.
    Petropoulos, Nikolaos
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mihaylov, Dimitar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    A Suggested Method for the Study of Crushed Aggregate Response to Dynamic Compaction2017Ingår i: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 22, nr 02, s. 387-406Artikel i tidskrift (Refereegranskat)
    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.

  • 4.
    Petropoulos, Nikolaos
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Crushed aggregate response upon impact in dry and wet conditions2017Ingår i: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 7, nr 3, s. 1-22Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Petropoulos, Nikolaos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser. Luleå University of Technology.
    Improved understanding of sublevel blasting: Determination of the extent of the compacted zone, its properties and the effects on caving2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Sublevel caving (SLC) is a mass mining method relying on the flowability of the blasted material. The ore is blasted in slices against caved material which is mainly waste rock. The result of the confined blast is greatly influenced by the interaction between the blasted material and the caved material. During blasting both materials change characteristics; the blasted material increases its porosity and compressibility due to breakage and swelling while the caved material is compacted and decreases in porosity and compressibility. The understanding of the mechanisms involved in this process is of significant importance.

    The behavior of the caved material (confining material) was studied in laboratory under dynamic loading. A new apparatus was developed to conduct impact tests to simulate blasting conditions. The tested material was a blend of crushed waste rock from drift development in the Kiirunavaara mine with maximum particle size 32 mm. The material was tested for two conditions, i.e. dry and wet (pendular state), and with different impact velocities (low (5 m/s), medium (8 m/s) and high (10-12 m/s)). During the impact tests, two types of measurements were taken; dynamic measurements based on the recordings from the installed accelerometers on the machine and static measurements pre- and post-impact. Additionally, the angle of repose, the impact duration, and the fragmentation was measured.

    In addition to the laboratory tests, small-scale blasting tests were carried out to investigate the burden behavior in confined conditions. The blasted specimen was a cuboid magnetic mortar block and the confining material was crushed concrete with maximum particle size 16 mm. The blocks were instrumented with custom-made incremental displacement sensor.

    After the analysis of the results from the above experimental work, two confined pillar tests (test #1 and test #2) were carried out at the Kiirunavaara mine. The preparation work for the pillar tests involved the development of instrumentation and installation techniques. The experimental configuration contained two blastholes and measurement holes in between the blastholes drilled from the neighboring drift. Test #1 mainly focused on the evaluation of the instrumentation and techniques while test #2 was focused on the interaction between the blasted burden and the confining material. The confining material in test #1 was a blend of ore and waste material from drift development at the Kiirunavaara mine. The characteristics of the material were unknown. Test #2 was split into two parts, the confining material in the first part was the same as in the laboratory impact tests and the second part of the pillar was confined by caved masses.

    The instrumentation was installed in the burden of the pillars and was equipped with accelerometers and displacement sensor. Additional instrumentation was also installed in the confining material.

    The burden in the small-scale blasting tests reached maximum velocity 29 m/s and maximum displacement 12.6 mm. In pillar tests, the burden movement was in the range of 0.9 to 1.1 m. In both pillar tests, burden erosion material was observed in the gap between the intact and the blasted burden. This material was finer compared to the blasted burden. The origin of this material was from the vicinity of the blastholes.

    The results of the laboratory tests showed that the wet material exhibited larger compaction zone than that of the dry material. The wet material showed apparent cohesion close to the impact surface of the tested material. A similar observation was made in test #2 where an agglomeration of the confining material, as a result of apparent cohesion, was observed on the surface of the blasted burden. The displacement data from the instrumentation in the burden and inside the confining material showed that the compaction zone follows an inverse exponential behavior. After the blast steeper angles of repose were measured indicating higher frictional forces between the particles. Moreover, the evidence of apparent cohesion and a larger angle of repose indicated the introduction of tensile strength in the material.

    The mass of the confining material was compressed elastically and plastically during the blast. After the blast, the material recovered its elastic deformation and pushed the blasted burden backward as observed in the small-scale blasting tests and the pillar tests. At this stage, the burden erosion material was compacted. Hence, there were 3 materials, i.e. burden erosion material, burden and confining material, which were compacted with different compaction rates. This condition promotes interlocking of the particles in the materials. If this behavior is correlated with a production SLC ring, then it indicates disturbances in flowability of the blasted material.

  • 6.
    Niklasson, Bengt
    et al.
    Geosigma.
    Olsson, Mats
    EDZ Consulting AB.
    Beyglou, Ali
    Swebrec.
    Petropoulos, Nikolaos
    Swebrec .
    Inspänningens Betydelse för Vibrationsnivån: Etapp 2 Fältförsök2016Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Blasting in urban areas must involve techniques to control the vibration level. Charge confinement is one of the parameters that are believed to influence the vibration level. A charge could be too confined due to:- Incorrect charge calculation (charge weight is too small for the drilled burden)- Incorrect interval-time (holes behind are initiated before holes ahead)- Incorrect selection of explosive for the burden or an influence of dead pressing- Unfavourable selection of geometry- Drill hole deviationA common opinion among blasters is that an increased confinement results in a higher vibration level. Is there a physical explanation for this or is it just a common misunderstanding established a long time ago? A feasibility study was previously conducted and reported in BeFo Report 132, (Niklasson et.al, 2014). The report comprised a literature study and an assessment of a number of observed misfires in tunnels, still with correctly detonating charges but with a reduction of more than 50 % in pull or rock breakage. It also comprised a statistical analysis of some of the rounds. The result of the study found no evidence for a relationship between degree of charge confinement and vibration level.As a result of the feasibility study a field study was proposed. This study was performed in a quarry, some 40 km north of Stockholm, close to Arlanda airport. A number of single holes were blasted; both holes with full breakage and confined holes and the vibration levels were measured.13 single holes with full breakage and 10 totally confined single holes were blasted. The burden was 1.5 m for the holes with breakage and the confined holes had a distance to the free surface of some 15 m. The hole diameter was 45 mm and hole depth 3 m. The holes were charged with a dynamite explosive, Minex Eco, and the charge weight was 1 kg/hole. The charges were initiated with electric detonators. All holes were stemmed.The vibration levels were measured in three holes with a depth of 3 m. In the bottom of the holes thee-axial geophones were grouted. A forth geophone was placed on the surface.Single hole blasting were performed with very good result. The holes close to the surface gave full breakage while the confined holes showed no breakage.The vibration signals were vector summarised and analysed. The distances from each hole to each geophone was determined. The vibration PPV-values were plotted as a function of the distances.The final result showed that there were no significant differences in vibration levels between confined holes and holes with full breakage.Key words: Vibrations, confined holes, blasting, geophones, grouting, quarry

  • 7. Wimmer, Matthias
    et al.
    Nordqvist, Anders
    Mining Technology R and D, LKAB Kiruna Mine.
    Righetti, Edoardo
    Petropoulos, Nikolaos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Thurley, Matthew
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system. Innovative Machine Vision.
    Analysis of rock fragmentation and its effect on gravity flow at the Kiruna sublevel caving mine2015Ingår i: 11th International Symposium on Rock Fragmentation by Blasting: FragBlast11, Carlton VIC: The Australasian Institute of Mining and Metallurgy, 2015, s. 775-791Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fragmentation in sublevel caving (SLC) is vitally important. Both gravity flow and any downstreamprocesses are affected. Fairly coarse fragmentation may lead to larger draw bodies (isolatedextraction zones) and hence potentially higher primary ore recovery and depressed/delayedwaste rock inflow from above. Fewer flow disturbances are expected by mitigating oversize. Inaddition, it requires less boulder handling and reduces wear and possible hang-up problems inorepasses. To assess the present-day functionality of large-scale SLC, a multiyear, comprehensivemeasurement program was initiated. It covers the main elements for SLC, namely blast function,fragmentation and gravity flow. The present paper focuses on fragmentation measurements. Animage acquisition system was used to document the drawpoint and the load-haul-dump (LHD)bucket for each mucking cycle. At the beginning, four buckets (about 70 t total) were sieved tovalidate the results of both 2D and 3D image analysis techniques. The fundamental and specificproblems are discussed herein. At the moment, fragmentation of the SLC rings is evaluated usinga quick rating system and a 2D fragment delineation software. The results enable a descriptionof fragmentation and its variation during mucking but also – combined with the gravity flowmeasurements – conclusions on the fragmentation for different parts of the SLC ring. Possibleinfluences on flow disturbances and ore recovery/dilution are investigated. The recent findingsallow a better understanding of breakage and flow and support future process improvements.

  • 8.
    Petropoulos, Nikolaos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Burden Dynamics and Fragmentation2015Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Drill and blast is a dominant technique in several surface and underground mines in the world. The purpose of this technique is to break rock mass into fragments, which can be handled by mining equipment. The identified major influencing factors in rock blasting are stress waves and gas pressurization. In underground mines, especially in sublevel caving mines, the blast is performed under confined conditions. Hence, one more category of mechanisms has to be taken into consideration which describes the behavior of granular materials. Several small-scale tests have been conducted in order to define parameters which affect fragmentation by blasting as well as to measure the burden behavior during blasting. The purpose of these tests was to investigate how firing pattern, confinement and inter-hole delay time influence the fragmentation. Additionally, an incremental relative distance sensor was developed to measure the burden movement during blasting. The results showed that the burden moved with a velocity of approximately 29 m/s. The V-shaped firing pattern gave coarser fragmentation compared with sequential firing pattern for both the blasted material and confining material.After the small-scale tests, a zero pillar test was conducted under confined conditions to evaluate and validate a newly developed measuring system. The purpose of this system was to measure the burden dynamics. The system was calibrated in laboratory conditions under dynamic loading. This system was based on a piston-like structure and it was equipped with accelerometers and a potentiometric distance sensor. In addition to the measuring system, several installation and initiation procedures have been developed. The results of the measuring system showed that the burden moved 0.98 m at a velocity of 17-18 m/s. All the procedures performed as well as expected and designed.In addition to the study of blasting related mechanisms, the results of a blast also have to be measured. Sieving is usually not an option for large scale operations due to high costs. The alternative way is to implement digital image analysis. This procedure does not interfere with the production of a mine. Several trials have been conducted at the Aitik open pit mine to investigate the influence of short inter-hole delay time (1 ms, 3 ms and 6 ms or 0.14 ms/m burden, 0.43 ms/m burden and 0.86 ms/m burden) on fragmentation. The examined mechanism was the interaction of stress waves between neighboring blastholes. The fragmentation results showed that the trial with 3 ms inter-hole delay time gave a finer fragmentation by 10 % compared with reference blasts and other trials. However, there was an indication that the large specific charge at the mine overshadows the stress wave interaction mechanisms.An additional set of trials was conducted at the Kiruna mine to investigate the gravity flow of broken material. The fragmentation measurements were done with SplitDesktop®. This is a digital image analysis software which calculates fragmentation based on a delineation process of the particles in an image. The aim of in these trials was to develop a procedure to minimize the image editing time. The application of ‘Unsharp Mask’ filter improved the image quality and enhanced the contrast between the particles combined with a quick rating system (developed by LKAB) so that the image processing time was significantly reduced from 2 hours to 10-15 minutes.

  • 9.
    Petropoulos, Nikolaos
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mihaylov, Dimitar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Wimmer, Matthias
    Nordqvist, Anders
    Mining Technology R and D, LKAB Kiruna Mine.
    Design of equipment for dynamic burden measurements2015Ingår i: 11th International Symposium on Rock Fragmentation by Blasting: FragBlast11, Carlton VIC: The Australasian Institute of Mining and Metallurgy, 2015, s. 493-500Konferensbidrag (Refereegranskat)
    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.

  • 10.
    Nyberg, Ulf
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Klippmark, Victoria
    LKAB.
    Karlström, Hans
    LKAB.
    Beyglou, Ali
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Petropoulos, Nikolaos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Short time measurements of toxic fumes from detonation of emulsion explosive: Initial tests in blast chamber2015Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Spränggaser uppmätta med hjälp av en rökgasanalysator och detonationshastigheten VoD rapporteras för 18 tester utförda i en 35 m3 sprängkammare under en vecka juni 2014. Testerna för Swebrec:s syrebalanserade rena E682 och E682 med inblandning av Al eller torra ANprills i glasrör visar att toxiska gaser (CO och NOx) generellt ökar för det rena emulsionssprängämnet med tillsatser av 5 % Al respektive 30 % torra ANprills. Vid jämförelse av blandningsemulsion med ren emulsion är CO en faktor 1,6–1,9 högre för tillsatser av 30 % torra ANprills. För NO varierar skillnaderna i ppm-värdena för både 5 % Al och torra 30 % ANprills med laddningsdiameter; förhållandet varierar från ca 1,3 för Ø65,6 mm laddningar till ca 2,8 för Ø27,0 mm laddningar vilket tyder på en snabbare och effektivare förbränning för de större laddningsdiametrarna. VOD mätningarna visar för E682 ökande värden med laddningsdiametern. Den producerade volymen CO och NO per kg sprängämne ökar med minskande laddningsvikt (diameter) vilket kan tolkas som att förbränningen är effektivare med ökande diameter.Det finns också en avtagande trend för NOx-värden över tiden som sannolikt kan förklaras som ett resultat av sekundär oxidation av NO till NO2 (2NO + O2 → 2NO2) när spränggaserna blandas med sprängkammarens atmosfär. De uppmätta O2 värden är ofta strax under 21 % efter sprängning men ytterligare något lägre för de större laddningarna.

  • 11.
    Petropoulos, Nikolaos
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Beyglou, Ali
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nyberg, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Novikov, Evgeny
    Boliden Mineral AB.
    Fragmentation by blasting through precise initiation: Full scale trials at the Aitik Copper mine2014Ingår i: Blasting and Fragmentation, ISSN 1937-6359, Vol. 8, nr 2, s. 87-100Artikel i tidskrift (Refereegranskat)
    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.

  • 12.
    Petropoulos, Nikolaos
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Beyglou, Ali
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Novikov, Evgeny
    Nyberg, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Improved blasting performance through precise initiation2013Ingår i: EFEE-7th World Conference on Explosives & Blasting, Moscow: European Federation of Explosives Engineers , 2013, Vol. 1, s. 20-26Konferensbidrag (Refereegranskat)
    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.

  • 13.
    Petropoulos, Nikolaos
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nyberg, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Novikov, Evgeny
    Beyglou, Ali
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Improved blasting results through precise initiation: results from field trials at the Aitik open pit mine2013Rapport (Refereegranskat)
    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.

  • 14.
    Petropoulos, Nikolaos
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Ouchterlony, Finn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Fragmentation under different confinement conditions and the burden behaviour: small scale tests2012Ingår i: 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, s. 61-70Konferensbidrag (Refereegranskat)
    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.

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