| 1. |
- Edelbro, Catrin, et al.
(author)
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Engaging with Program Stakeholders to Support Program Development
- 2017
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In: The 13th International CDIO Conference Proceedings - Full Papers. - Calgary.
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Conference paper (peer-reviewed)abstract
- Luleå University of Technology (LTU) has adopted CDIO as the framework for developing its engineering programs. At the Department of Civil, Environmental and Natural Resources Engineering, there are two programs focusing on tunnelling, mining and rock excavation. Despite very positive prospects for professionals in the field, the number of students has decreased for the last two years. Further, program content might not reflect recent developments or new requirements in the industry. Therefore, the programs and their courses are taken under renewed consideration. Given the nature of the challenges facing the programs, it is in this case particularly important to inform of the planned development through a dialogue with stakeholders. Stakeholder dialogue is also a key feature of a CDIO curriculum development (CDIO Standard 2). This paper reports on a process of engagement with industry representatives, initiated through a meeting to discuss the competence of newly graduated from LTU as well as the future needs in the industry. The input will make it more visible what programme and course development work needs to be done in the nearest future. A continued support and feedback from the industry is warranted during the programme development.
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| 2. |
- Eitzenberger, Andreas
(author)
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Inventory of geomechanical phenomena related to train-induced vibrations from tunnels
- 2008
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Licentiate thesis (other academic/artistic)abstract
- Banverket is expecting that the number of railway tunnels in densely populated areas will increase over the next 20 years due to the lack of available space on the ground surface, but also since the railway is considered an environmentally friendly solution of transportation for the future. The need for good predictions of vibration and noise levels in dwellings along the planned tunnels is therefore evident. Due to lack of understanding of the propagation of train-induced vibrations from tunnels in rock a research project has been initiated by Banverket. This thesis constitutes the first stage of that project. In this thesis, the propagation of vibrations through a rock mass has been reviewed. The emphasis has been on wave propagation in hard rock masses. Areas, such as the generation of vibrations at the train-rail interface, the response of buildings and humans, national and international recommended noise and vibrations levels, and possible countermeasures are briefly reviewed as well. Finally, suggestions for the continued research are presented. The propagation of waves is influenced by attenuation along the propagation path. The attenuation can either be through geometric spreading, energy loss within the material, or reflection and refraction at boundaries. In a rock mass, where heterogeneities of various scales are present, the attenuation of (train-induced) waves through the ground therefore mainly depends on the properties of the discontinuities. Theoretical models of wave propagation across individual fractures have been presented in the literature. These models can be used to study the attenuation at the fracture for different combinations of joint stiffness, impedance, and angle of incidence. Also multiple parallel joints can be theoretically analysed. The attenuation of low-frequency waves is more prominent in weak rock masses and virtually negligible for hard rock masses. An increased amount of random oriented joints, faults and boundaries increases the attenuation of the waves, but is not possible to study with the aid of theoretical models. The rock mass is in most cases inhomogeneous due to all heterogeneities present. Despite this fact, the rock mass and soil is always treated as an isotropic, homogeneous material in the analyses of ground-borne noise and ground-borne vibrations. This concerns both numerical and empirical methods. Thus, there is a lack of a method that considers the influence of various heterogeneities present in a rock mass on the propagation of waves. Future research regarding train-induced vibrations should focus on combining the models of attenuation in the material with the models of attenuation across joints. Thereafter, conceptual models should be used to determine the propagation of low-frequency waves in a rock mass containing various amounts of heterogeneities (from isotropic to highly inhomogeneous) which should be compared to the theoretical methods available. Once the behaviour of waves in an inhomogeneous rock mass has been established, conceptual models should be used together with measurements from a few well documented cases. From the results of the analysis, guidelines for analysis of railway tunnels with regard to ground-borne noise and ground-borne vibrations should be established.
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| 3. |
- Eitzenberger, Andreas, et al.
(author)
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Numerical simulation of train-induced vibrations in rock masses
- 2012
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In: Harmonising rock engineering and the environment. - Leiden : CRC Press/Balkema. - 9780415804448 ; , s. 1189-1194
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Conference paper (peer-reviewed)abstract
- The vibrations generated by a moving train in a tunnel will radiate into the surrounding ground which, in densely populated areas, will reach nearby buildings and its residents. Analyses are commonly made where the aim is to estimate the ground-borne noise and vibrations levels that may occur in nearby buildings. A common assumption is to treat the rock mass as an isotropic, homogeneous, and linear elastic material. Thus, the influence of discontinuities on the propagation of waves is not considered in the analyses. Within this study, numerical simulations were performed to study the propagation of low-frequency waves through a rock mass near a tunnel. A single period sinusoidal wave was applied as dynamic source on the floor of the tunnel. Observation points were located on the ground surface and around the tunnel. The influence on wave propagation from overburden, position of a discontinuity in relation to the tunnel, and normal and shear stiffness of the discontinuity, was studied by using the Universal Distinct Element Code (UDEC). The results show that increasing overburden reduces the vibration levels on the ground surface. Furthermore, the influence of the normal and shear stiffness of discontinuities depends on where the horizontal discontinuity is positioned in relation to the tunnel. If the horizontal discontinuity is positioned above the dynamic source (e.g. above tunnel or in the tunnel wall) the vibration levels on the ground surface will be reduced but if the horizontal discontinuity is located below the dynamic source (e.g. below the tunnel) the vibration levels on the ground surface will be enhanced. In our analyses, discontinuities only have an impact on the wave propagation if the normal and shear stiffness of is ≤10 GPa/m.
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| 4. |
- Eitzenberger, Andreas
(author)
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Train-induced vibrations in tunnels : a review
- 2008
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Reports (other academic/artistic)abstract
- Banverket is expecting that the number of railway tunnels in densely populated areas will increase over the next 20 years due to the lack of available space on the ground surface. Together with the increased awareness of the residents the need for good prediction of vibration and noise levels in dwellings along the planned tunnels is evident. Consequently, a study of the propagation of vibrations through rock and soil generated by trains operating in tunnels is required in order to make more reliable prognoses. This report constitutes the first stage within a research project aimed at increasing the understanding about ground-borne noise and ground-borne vibrations generated by trains moving in tunnels constructed in rock. In this report, the propagation of vibration through a rock mass is reviewed. The emphasis has been on wave propagation in hard rock, but soil has also been included. Areas, such as the generation of vibration at the train-rail interaction, the response of buildings and humans, national and international recommended noise and vibrations levels, measurement of noise and vibrations, and possible countermeasures are briefly reviewed as well. Finally, suggestions for the continued research within this field are presented. The propagation of waves is influenced by attenuation along the propagation path. The attenuation can either be through geometric spreading, energy loss within the material, or reflection and refraction at boundaries. In a rock mass, where heterogeneities of various scales are present, the attenuation of (train-induced) waves through the ground therefore mainly depends on discontinuities, e.g. joints, faults, cracks, crushed zones, dykes, and boundaries between different rock types or soil. Also the topography - along as well as intersecting tunnels - influences the wave propagation in form of local amplification. An increased amount of joints, faults and boundaries increases the attenuation of the waves. The rock mass is in most cases inhomogeneous due to all heterogeneities present. Despite this fact, the rock mass and soil is always treated as an isotropic, homogeneous material when analyzed with regard to ground-borne noise and ground-borne vibrations. This concerns both numerical and empirical methods. Thus, there is a lack of knowledge regarding the influence of various heterogeneities on the propagation of waves, and thereby vibrations, in non-isotropic ground conditions (e.g. a rock mass) at low frequencies. Future research regarding train-induced vibration should focus on conceptual models used to determine the propagation of low-frequency waves in a rock mass containing various amount of heterogeneities (from isotropic to highly inhomogeneous). Once the behaviour of waves in an inhomogeneous rock mass has been established, conceptual models should be used together with measurements from a few well documented cases. From the results of the analysis, guidelines for analysis of railway tunnels with regard to ground-borne noise and ground-borne vibrations should be established.
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| 5. |
- Eitzenberger, Andreas
(author)
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Vågutbredning i berg
- 2013
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In: Föredrag vid Bergmekanikdag i Stockholm, 11 mars 2013. - Stockholm : Stiftelsen bergteknisk forskning - Befo. ; , s. 115-126
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Conference paper (other academic/artistic)abstract
- I tätbefolkade områden kan vibrationer genererade av tågtrafik i tunnlar nå närliggande byggnader i form av stomljud och/eller vibrationer. Tillförlitliga prognoser för att säkerställa att de som vistas i byggnaderna inte ska störas är nödvändigt när man planerar en ny järnväg eller bygger nya byggnader längs en befintlig järnväg. Numeriska analyser är idag en naturlig del vid prognostisering av tåginducerade vibrationer/stomljud. Vid analyserna antas ofta marken bestå av ett homogent och isotropt material. Vågutbredning genom diskontinuerliga bergmassor har studerats med hjälp numeriska analyser för att bedöma om ett sådant antagande är rimligt. Resultaten visar att sprickor under vissa förutsättningar påverkar vibrationerna lokalt på markytan ovanför en tunnel utsatt för en dynamisk last. Egenskaper som har stor inverkan på vågutbredning är sprickans normal och skjuvstyvhet, sprickors orientering och antal samt sprickavståndet. Zoner kan kanalisera vågor vilket resulterar i ökade vibrationer på markytan där zonen når markytan, men kan också agera som en vågfälla eller ett filter. Om det översta skicket av bergmassan har egenskaper som skiljer sig från den omgivande bergmassan förstärks generellt vibrationerna på markytan, särskilt i horisontell riktning.
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| 6. |
- Eitzenberger, Andreas
(author)
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Wave propagation in rock and the influence of discontinuities
- 2012
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Doctoral thesis (other academic/artistic)abstract
- This thesis concerns wave propagation in rock as a tool for determination of rockproperties and as a consequence of activities, such as trains.Using waves as a tool often means that rock properties are determined or the interior of a sample is studied without being damaged. Another use of waves is to measure the velocities in rock samples shaped as cubes, spheres or cores with plane and parallel end surfaces in order to determine if the rock is anisotropic; an important property to for example for the evaluation of stress measurements. The preparation of such samples are rather time consuming and costly, especially if many measurements have to be carried out. To overcome this obstacle diametrical measurements on drilled rock cores have been evaluated as a possible method to detect anisotropy. Measurements have been performed on metal cores, isotropic and anisotropic rock cores as well as rock cores containing microcracks. The results show that the technique is able to detect anisotropy caused by both geological composition and microcracks having a preferred orientation. However, in order to be detected the anisotropy must be parallel or sub-parallel to the core axis.Furthermore, diametrical measurements on cores retrieved from the rock mass beneath a drift showed that the anisotropy decreased while the P-wave velocity increased with increasing distance from the drift floor. Microcracks with a preferred orientation were developed either during excavation or by the increased stresses around the drift. Waves as a consequence of activities are generally considered as something negative, for example, vibrations radiating from underground railways. In densely populated areas these vibrations reach nearby buildings and the residents as ground-borne noise and/or vibrations. Reliable predictions to ensure that residents will not be annoyed are a necessity when planning a new railway or constructing new buildings along an existing route. Numerical analysis is a natural part of the prediction models for train-induced vibrations. In general these analyses treat the ground as homogeneous and isotropic. To determine if such an assumption is valid wave propagation through discontinuous rock masses have been studied using numerical analyses. The results of the analyses show for example that discontinuities can significantly increase the vibrations locally on the ground surface above a dynamically loaded tunnel. Properties having the greatest impact on wave propagation are the shear and normal stiffness of the discontinuity, the number of discontinuities and their internal distance, angle of incidence and the frequency of the wave. This study shows that discontinuities under certain conditions have an impact on the propagation of train-induced vibrations. Zones with a non-zero thickness show some other interesting phenomena, for example: they can result in channelling of waves resulting in higher velocity-levels at the ground surface where the zone daylights but also as a wave trap or filter. If the uppermost part of the rock mass has properties different from those of the host rock mass, generally amplifies the peak particle velocity on the ground surface especially in the horizontal direction.
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| 7. |
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| 8. |
- Svartsjaern, Mikael, et al.
(author)
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Conceptual Numerical Modeling of Large-Scale Footwall Behavior at the Kiirunavaara Mine, and Implications for Deformation Monitoring
- 2016
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In: Rock Mechanics and Rock Engineering. - : Springer Science and Business Media LLC. - 0723-2632 .- 1434-453X. ; 49:3, s. 943-960
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Journal article (peer-reviewed)abstract
- Over the last 30 years the Kiirunavaara mine has experienced a slow but progressive fracturing and movement in the footwall rock mass which is directly related to the sublevel caving (SLC) method utilized by Luossavaara-Kiirunavaara Aktiebolag (LKAB). As part of an on-going work, this paper focuses on describing and explaining a likely evolution path of large-scale fracturing in the Kiirunavaara footwall. The trace of this fracturing was based on a series of damage mapping campaigns carried out over the last two years, accompanied by numerical modelling. Data collected from the damage mapping between mine levels 320 and 907 m was used to create a 3D surface representing a conceptual boundary for the extent of the damaged volume. The extent boundary surface was used as the basis for calibrating conceptual numerical models created in UDEC. The mapping data, in combination with the numerical models, indicated a plausible evolution path of the footwall fracturing that was subsequently described. Between levels 320 and 740 m the extent of fracturing into the footwall appears to be controlled by natural pre-existing discontinuities, while below 740 m there are indications of a curved shear or step-path failure. The step-path is hypothesised to be activated by rock mass heave into the SLC zone above the current extraction level. Above the 320 m level the fracturing seems to intersect a sub-vertical structure that daylights in the old open pit slope. Identification of these probable damage mechanisms was an important step in order to determine the requirements for a monitoring system for tracking footwall damage. This paper describes the background work for design of the system currently being installed.
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| 9. |
- Svartsjaern, Mikael, 1986-, et al.
(author)
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Determination of magnitude completeness from convex Gutenberg-Richter graphs in the central portion ofthe Kiirunavaara mine
- 2017
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In: Journal of the Southern African Institute of Mining and Metallurgy. - : South African Institute of Mining and Metallurgy. - 2225-6253 .- 2411-9717. ; 117:6, s. 545-560
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Journal article (peer-reviewed)abstract
- This paper describes a study of seismic records from the Kiirunavaaramine footwall which were interpreted in relation with numerical modelsdeveloped outside the study. Seismic data was retrieved from a portion ofthe mine and filtered with respect to the ratio between energy carried byan event's P (primary) and S (secondary) waves (Es/Ep ratio), localmagnitude, and active mining depth. The data was analysed using Es/Epratios and Gutenberg-Richter graphs to determine the event origin,mechanisms, and minimum magnitude cut-off. The magnitudecompleteness was identified by studying the b-value stability and b-valuedifferentiation between origin sets. It was shown that, by separatingseismic events into the origin components shear, complex, and tensilebased on Es/Ep ratios, a representative value for the magnitudecompleteness can be identified for a catalogue with a convex cumulativelog curve. The majority of the events were shown to be of shear-slip originbased on the recorded Es/Ep ratios, with pure tensile events constitutingonly about 10% of the recorded data. Spatial and temporal event locationpatterns were studied and compared with numerical modelling results. Thecomparison showed a correlation between shear-slip seismic events andvolumes experiencing high differential stresses in the lower part of thefootwall. In the upper part of the footwall the results did not reveal anyclear correlation between observed damage in drifts and seismic eventlocations. The concentration of seismic events in the lower portion of thefootwall is discussed in the context of rock mass displacements. Theresults indicate a possible connection between mine seismicity at depthand damage observations in the drifts in higher non-seismic areas byseismic softening and subsequent lateral expansion of the rock mass.
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| 10. |
- Svartsjaern, Mikael, 1986-
(author)
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Footwall stability in SLC mining
- 2017
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Doctoral thesis (other academic/artistic)abstract
- This thesis is based on a case study of the Kiirunavaara sublevel cave (SLC) mine. It focuses on footwall stability and damage development in the mining infrastructure on mine scale. Damage to the infrastructure is mappable for the full height of the footwall by access through decommissioned infrastructure associated with earlier mining stages. Damages range from pure structurally controlled failures (wedge failures) in the upper part of the footwall to fracture growth through intact rock combined with micro‑seismic emissions at the active mining depth.The thesis addresses four distinct research questions;(i) What are the predominant failure mechanisms for the Kiirunavaara footwall?(ii) What is the role of confinement on the damage development in the footwall?(iii) How does the SLC relate to the footwall damage development?(iv) How can infrastructure damage associated to the future mining be estimated using currently available data?Two sets of calibrated numerical models were used to study the damage evolution processes using damage mapping data as the main calibration parameter. Validation of the models was achieved by correlation of model output to micro-seismic locations. The modelling and damage mapping results were used as the basis for the development of a simple prognosis tool for estimating the ultimate extent of infrastructure damage associated to the mining advance for future mining steps.A literature review on slope failure modes, large scale failures in cave mining and failure tracking using micro-seismic locations is included to provide background and definitions. The literature describes principal failure modes as well as mechanism combinations such as structurally controlled failures initiated by deep seated rock mass failures or relaxation. Cases are presented where previously stable structures become destabilised by cave advance and examples where micro‑seismic recordings were used to track deformations and the initiation and growth of newly formed fractures.The Kiirunavaara SLC mine is presented in detail as the main case study of the work. The mine has been in operation since the early 20th century with a transition to underground operation over 50 years ago. The extent of the orebody is 4 km in length with an average width of 80-90 m, the termination at depth has yet to be determined. The ore has an average dip of 60˚ east and a dip-along-strike to the north. Both the footwall and hangingwall rock masses are considered hard and competent with UCS values for the footwall ranging from ca. 130 MPa to extreme cases of 600 MPa. The ore is mined in production blocks about 400 m wide (along strike), Mining of the northernmost blocks, situated in the Lake ore, did not start as open pit operations but has been accessed from the underground via SLC only.The instabilities in the footwall has been addressed by several research studies in the past, with the predominant failure mechanisms in different studies being suggested as large scale tensile failure, complex wedge failure, or rotational shear failure, i.e., some type of principal slope failure.In this work, conceptual numerical models in UDEC were calibrated to fit underground damage mapping data by tracking numerical shear strain concentrations. The conceptual models suggested rock mass damage without the indications of development of large scale slope failure mechanisms such as shear bands. Mine scale PFC models were calibrated with respect to the rock mass strength parameters derived by the conceptual UDEC models and used to study rock mass fracturing in the absence of large scale failure. It is shown that damage to the rock mass occurs mainly close to the active mining in a seismically active zone. This is suggested to weaken and soften the rock mass to allow the development of infrastructure damage in this volume to occur as the rock mass relaxes when entering the stress shadow of the SLC as mining progresses.The damage to the rock mass at the production depth is argued, based on seismic records and a parametric study in UDEC, to constitute of large quantities of local shear failures coalescing to appear as a large scale step-path or rotational shear failure in mapping records. The extent of the associated infrastructure damage is predicated to be limited by the extent of the damaged rock mass zone. A simple bi-linear equation is suggested using ore-width and mining depth as input to estimate the ultimate extent of the damaged zone for each mining stage and thus the limit of later infrastructure damage development.The thesis is concluded with recommendations for future work and potential for continued research.
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