| 31. |
- Andrén, Anna, et al.
(författare)
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Evaluation of a laboratory model test using field measurements of frost penetration in railway tunnels
- 2022
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Ingår i: Cold Regions Science and Technology. - : Elsevier. - 0165-232X .- 1872-7441. ; 204
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Tidskriftsartikel (refereegranskat)abstract
- Despite extensive grouting efforts to prevent water from leaking into tunnels, water seepages remain. When exposed to freezing temperatures, ice formations occur. During the winter, the Swedish Transport Administration's railway tunnels are affected by major problems caused by ice, such as icicles from roof and walls, ice loads on installations, ice-covered tracks and roads, etc. To ensure safety and prevent traffic disruptions, many tunnels require extensive maintenance. Improved knowledge about frost penetration in tunnels is required to reduce maintenance of the tunnels. Frost insulated drain mats are often used at leakage spots to prevent ice formation along the tunnels. To find out which parts of a tunnel are exposed to freezing temperatures, the University of Gävle and the Royal Institute of Technology in Stockholm conducted a laboratory model test on behalf of the Swedish National Rail Administration (now the Swedish Transport Administration). The laboratory model test aimed to find a method to determine the expected temperature conditions along a tunnel to decide which parts of the tunnel require frost insulation to protect the drainage system from freezing and prevent ice formation. To evaluate the laboratory model test, the Swedish Transport Administration in collaboration with Luleå University of Technology have performed field surveys in two Swedish railway tunnels. The field measurements involved monitoring temperatures in air, rock surfaces and rock mass, as well as measuring wind direction, wind and air velocity and air pressure. The measurements in the tunnels show that the frost penetrates further into the tunnels than was expected from the laboratory model test, which was based on a completely uninsulated tunnel. Frost insulated drains do not only prevent the cold air from reaching the rock mass, but also prevent the rock from emitting geothermal heat that warms up the cold tunnel air. Consequently, the frost penetrates further into the tunnel than it would do if the heat from the rock mass was allowed to warm up the outside air on its way into the tunnel. The number of frost insulated drains and how much of the tunnel walls and roof are covered thereby affect the length of the frost penetration.
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| 32. |
- Bjurström, Henrik, et al.
(författare)
-
Comparative Seismic Laboratory and Non-Contact Field Measurements of Asphalt Concrete
- 2016
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Ingår i: 2016 Structural Materials Technology Paper Summaries.
-
Konferensbidrag (refereegranskat)abstract
- Non-contact acoustic field measurements are performed on a newly built highway to characterize the real part of the dynamicmodulus of the asphalt concrete (AC) top layer. The in situ measurements are performed using an array of 48 micro-electromechanicalsystem (MEMS) sensors. Cores extracted from the field measurement positions are then examined in a laboratory usingseismic modal testing for comparison. The laboratory testing allows master curves to be constructed to characterize the AC over awide temperature and frequency range. It is demonstrated that the real parts of the dynamic moduli are consistent at the fieldtemperatures using the two test methods. The in situ measurements are also shown to be highly repeatable. The presentedcomparative study indicates a possible application for assuring the quality of AC based on mechanical properties using fast noncontactin situ measurements.
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| 33. |
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| 34. |
- Dineva, Savka, et al.
(författare)
-
Evolution of seismicity at Kiruna Mine
- 2017
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Ingår i: Deep Mining 2017. - Perth : Australian Centre for Geomechanics. - 9780992481063 ; , s. 125-140
-
Konferensbidrag (refereegranskat)abstract
- Kiirunavaara (Kiruna) iron ore mine owned by LKAB (Sweden) is one of the largest underground mines. Miningstarted in 1898 as an open pit mine. In mid-1950, the mine started a transition to underground mining andpassed to only underground mining in 1962. More substantial problems with seismicity started in 2007-2008when the deepest mining level was 907 m (ca. 670 m below surface). By 2016, the mining production is at1,022–1,079 m Level (ca. 785–845 m below surface). More than one billion tonnes of ore have been extractedsince the beginning of mining. The average yearly production in recent years is 28 million tonnes.By 2016 the mine has the largest underground seismic system in the world with 204 operational geophones.The number of the sensors (geophones with natural frequencies of 4.5, 14, and a few of 30 Hz) changed withthe increasing of production depth. The major stages with seismic system upgrades are: August 2008–June2009 with 112 installed geophones, and July 2012–September 2013 with 95 installed geophones. During2016–2017 it is planned to install some additional 45 geophones.The study was carried out to identify some trends in seismicity as the mining goes deeper and to find thecorrelation with some main controlling parameters – volume and depth of the production in order to obtaininformation for future seismic hazard and risk analysis. Custom made applications within mXrap were utilisedto carry out the spatial variations of seismicity.The analysis showed substantial difference between the seismicity in the three studied blocks – 15/16, 28/30,and 33-37/34, with the weakest seismic activity in Block 15/16 (Mmax 1.6, maximum observed magnitude),followed by Block 28/30 (Mmax 2.2), and then largest seismicity in Block 33-37/34 (Mmax 2.2). The dailyseismicity rate increased substantially through the years only for Block 33-37/34. The seismicity correlatesstrongly with the production depth. In general a straightforward correlation between the production volumeand number of larger events (M > 0) was not found for the three studied blocks, assuming there are otherfactors affecting the seismicity, e.g. geological structures, areas with contrast in geomechanical properties,etc. The spatial variations of some seismic source parameters were traced for varying periods of time,depending on the major production stages (opening of new levels, full production, closing) for the threeblocks. The distributions of the cumulative seismic energy showed a maximum around and below theproduction. The cumulative seismic moment and number of events in most cases showed a maximum aroundand above the production, indicating caving in these areas. The static stress drop shows the largest valuesaround and below the production on the footwall side, corresponding also to the areas with increased stress.The energy index showed increased stresses in the same areas (EI > 1).This study is only the first overview of the seismicity in Kiruna Mine. For seismic hazard assessment and riskanalysis further more detailed studies with smaller time intervals need to be carried out to obtain more precisecorrelations between the seismic parameters and the production volume and depth, and other possible factorsaffecting seismicity (geological structures, areas with contrast geomechanical properties, etc.).
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| 35. |
- Dineva, Savka, et al.
(författare)
-
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
-
Ingår i: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction. - 9789175838045
-
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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| 36. |
- Eitzenberger, Andreas
(författare)
-
Inventory of geomechanical phenomena related to train-induced vibrations from tunnels
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)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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| 37. |
- Eitzenberger, Andreas, et al.
(författare)
-
Numerical simulation of train-induced vibrations in rock masses
- 2012
-
Ingår i: Harmonising rock engineering and the environment. - Leiden : CRC Press/Balkema. - 9780415804448 ; , s. 1189-1194
-
Konferensbidrag (refereegranskat)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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| 38. |
- Eitzenberger, Andreas
(författare)
-
Train-induced vibrations in tunnels : a review
- 2008
-
Rapport (övrigt vetenskapligt/konstnärligt)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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| 39. |
- Fransson, Åsa, 1971, et al.
(författare)
-
An integrated approach to rock grouting
- 2018
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Ingår i: ISRM International Symposium - 10th Asian Rock Mechanics Symposium, ARMS 2018.
-
Konferensbidrag (refereegranskat)abstract
- Grouting of rock is a trans-disciplinary and trans-stadial topic. It is trans-disciplinary in the sense that grouting involves defining the geological and hydrogeological conditions and what to achieve at a specific site in relation to e.g. decrease in flow and hydraulic conductivity or maintaining ground water levels. Further, the grouting materials to be used to modify and improve the geological and hydrogeological conditions have to be characterised and have properties in line with both rheological and environmental demands. Hydrogeological conditions and grouting material properties in combination with analytical solutions allow estimates of penetration length, thus facilitating grouting design. Grouting is trans-stadial due to its importance in all stages from early planning to long term maintenance. In all stages, hydrogeological conditions and environmental impact are key issues. For the grouting design and construction a step-wise approach based on the observational method including prediction, observation and action is advantageous considering the uncertainties related to hydrogeological conditions and environmental impact. This paper aims at presenting theoretical development using a number of references and case studies to highlight the importance and usefulness of an integrated and theoretically based approach to grouting.
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| 40. |
- Ittner, Henrik, et al.
(författare)
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Investigation of blast fractures from mechanized charging with emulsion during tunnelling
- 2017
-
Ingår i: Proceedings of the World Tunnel Congress 2017. ; , s. 1542-1549
-
Konferensbidrag (refereegranskat)abstract
- Aquality factor that can decrease the need for rock reinforcement andmaintenance in underground facilities is limitation of blast damage in thetunnel contour. This paper presents results from a project initiated by the SKBand Forcit Sweden AB to investigate the extent of blast damage from emulsionexplosives. The investigations were conducted at two tunnel sites in Sweden,Äspö HRL and a wastewater tunnel under construction in Kista. The tunnels wereexcavated with the same technology for mechanized charging but with differentpurposes and quality requirements. Results from the presented project includefracture mapping of the excavated slots, blast fracture length and frequency,calculated charge concentration for mapped blasting halfpipes in the slots atÄspö HRL and measurements of VOD (velocity of detonation) in the wastewatertunnel in Kista and the Kankberg mine.
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