| 1. |
- Saiang, David, et al.
(författare)
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FLAC3D modelling of rock support arches
- 2020
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Ingår i: 5th International Itasca Symposium - 2020.
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Konferensbidrag (refereegranskat)abstract
- This paper presents the FLAC3D modelling of rock support arches in trial stope at Boliden's Garpenbergmine in Sweden. The objective was to evaluate the effectiveness of rock support arches in stabilizing theground when rill stopes heights are raised beyond the current heights. Boliden utilizes the Rill miningmethod to mine most of its orebodies that are hosted in poor ground conditions; weak rock and high stresses.This mining method requires the development lower and upper drifts and extracting the block of ore between the drifts by a sequence of benching, mucking and backfilling cycles. The block of ore between thetwo drifts is generally referred to as rill bench. Presently, the rill bench heights are restricted to 10-15 m soas not to expose the stopes to high walls comprising weak rock in high stress field. However, it has beenroutinely observed that, much of the ground deformations appear to occur during the early stages when thelower and upper drifts are developed and significantly diminish when the rill benches are mined. This observation gave the reason to investigate the possibility to raise the rill bench heights, with additional reinforcement provided by rock support arches. Boliden has successfully used rock support arches at theGarpenberg mine as well as in its other mines (Boliden 2016). The view is that, by installing optimallyspaced rock support arches, stable ground conditions can be achieved thereby permitting the rill benchheights to be raised to 20 or 25 m. To test this hypothesis a series of numerical models were run in FLAC3Dwith different rill heights and different arch spacings, along with regular support, to investigate the performance of the arches. These simulations also preceded the field trial to identify the optimum arch spacingand the likely outcome of the field investigations. The field trial itself is presently conducted in the orebodycalled Dammsjön at a depth of 890 m with a rill stope height of 25 m (i.e. 20 m rill bench plus one 5 mdrift). Monitoring of the trial stope is currently on-going. Some initial data from this monitoring have beenmade available for the first pass calibration of the FLAC3D models presented in this paper.
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| 2. |
- Dineva, Savka, et al.
(författare)
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Local seismic systems for study of the effect of seismic waves on rock mass and ground support in Swedish underground mines (Zinkgruvan, Garpenberg, Kiruna)
- 2016
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Ingår i: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction. - 9789175838045
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Konferensbidrag (refereegranskat)abstract
- Three local seismic systems were installed by August 2015 in deep underground mines in Sweden – Zinkgruvan Mine (Lundin Mining AB), Garpenberg Mine (Boliden AB), and Kiirunavaara Mine (LKAB) as part of a project for developing new methods for Evaluating the Rock Support Performance (ERSP, Vinnova). The areas were chosen within the most probable volumes where large rockbursts can be expected. The local systems were installed at mine levels between 730 and 1150 m in different mines. The horizontal extend of each instrumented areas is between 70 and 100 m. The seismic system in each mine is a combination of uni-axial and three-axial 4.5 Hz geophones installed on the surface, in shallow (~0.5 m) and deeper (6-9 m) boreholes in profiles across drifts. These profiles are in close proximity to profiles with extensometers, instrumented bolts, and observation holes. The seismic systems are manufactured and installed by the Institute of Mine Seismology (IMS). The aim of the seismic systems is to record the seismic events that occur in the vicinity of the instrumented areas and provide valuable data about the variability of seismic waveforms around the underground openings and changes when seismic waves approach them. Data is used to study: 1) the attenuation/decrease of the maximum ground velocity (PPV) with the distance, especially at small distances; 2) site effects, including maximum amplitudes, predominant frequency, and duration of the seismic signals, 3) the attenuation/amplification of the seismic waves approaching the underground opening. The final aim is to obtain new information that can be used for improved requirements for the rock support design in rockburst prone areas.The installation of the seismic systems started in May 2015 (Zinkgruvan Mine) and was completed by August 2015. They run mostly in triggered mode with initial automatic arrival time picking and source parameter calculation and subsequent manual processing of seismic event of interest. More than 200,000 seismic events with magnitude from -4.5 to 2.0 were recorded by December 2015. At present only a small portion of all data was processed manually and the procedures for processing of the events were developed on this subset. The first results from the monitoring showed that there are differences in the amplitudes and shape of the seismic signals recorded by the sensors installed in deeper borehole (behind the most blast-damaged zone (6 – 9 m)) and close to the surface (0.5 m) or on the surface of the openings. There are also differences between the waveforms recorded on the walls and the roof along the same profiles or on nearby profiles. Data from the investigated rockbursts showed maximum velocity recorded from a seismic events at close distances with magnitude larger than 0.5 in the order of 10 cm/s with clipping levels 10 – 20 cm/s.
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| 3. |
- Zhang, Ping, et al.
(författare)
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Establishment of experimental sites in three Swedish mines to monitor the in-situ performance of ground support systems associated with mining-induced seismicity
- 2016
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Ingår i: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction. - 9789175838045
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Konferensbidrag (refereegranskat)abstract
- In order to assess the performance of ground support components and systems when subjected to seismic activity and strong ground motion, Luleå University of Technology together with three Swedish mining companies (Lundin Mining, LKAB and Boliden) started a three year research project in September 2014. The aim of the project is to develop new methods for evaluating the rock support performance in-situ that use all available information about i) the source of the seismic event (obtained from the seismic network in the mine and additional seismic sensors), ii) seismic loading (ground motion) recorded by temporary local seismic networks, and iii) the consequences of the seismic loading in terms of damage to the underground excavations and the rock support.The sites with high potential of seismic damage were defined after the historical damaging seismic events were reviewed and the mining-induced stress disturbance was investigated with 3D numerical models. As of 31 December 2015, four sites in three different mines have been instrumented. Geophones (in depth and at surface), multi-points extensometers and instrumented bolts were installed to monitor the ground motion, the deformation of the rock mass and the elongation of the bolts. Observation boreholes were drilled to investigate the rock lithology, structures as well as fracture distribution and development. The data from locally installed geophones will be integrated with seismic data recorded by the mine-wide network. For each monitoring point, all of the instruments and observation boreholes were located at very close area within 0.5-1 m distance from each other. These results will be used to establish the relationship between the dynamic loading and the response of rock mass and rock bolts. Additionally, laser scanning is used to measure the surface deformation of the whole volume of instrumented sites with time. Two damaging seismic events occurred near the instrumented sites after the instruments were installed and the results of site investigation show that installed instruments have captured the response of the rock mass and bolts due to production blasting and seismic events.
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| 4. |
- Kullerstedt, Margareta, et al.
(författare)
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Hur ser ungdomar på naturvetenskap? : Projektarbete. NOT-projektet.
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Vi presenterar en kartläggning av 13-åringars attityder till och erfarenheter av naturvetenskap och teknik. Det visar sig att ungdomarna prioriterar tid för familj och vänner samt ett intressant arbete. I skolan vill de lära sig om dinosaurier, vulkaner, åska och hur djur kommunicerar. Kunskaper som ljus-optik och hur tvättmedel fungerar kommer längst ner på popularitetslistan. Det tyder på att innehållet i NO-undervisningen bör förändras. Eleverna anger jämförelsevis få ämnen de vill lära sig mer om och det visar att skolan måste konkurrera om utrymmet i det moderna informationssamhället Flickorna visar större tilltro till forskning och vetenskap än pojkarna. De är mindre oroliga för att vetenskapen ska påverka vår miljö negativt eller skapa problem för samhället. Pojkarna tycker i högre grad än flickorna att vetenskap är intressant och spännande, men oroar i gengäld för dess skadeverkningar.
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