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| 2. |
- Sundell, Jonas, 1984, et al.
(författare)
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Economic valuation of hydrogeological information when managing groundwater drawdown
- 2019
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 27:4, s. 1111-1130
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Tidskriftsartikel (refereegranskat)abstract
- © 2019, The Author(s). A procedure is presented for valuation of information analysis (VOIA) to determine the need for additional information when assessing the effect of several design alternatives to manage future disturbances in hydrogeological systems. When planning for groundwater extraction and drawdown in areas where risks—such as land subsidence, wells running dry and drainage of streams and wetlands—are present, the need for risk-reducing safety measures must be carefully evaluated and managed. The heterogeneity of the subsurface calls for an assessment of trade-offs between the benefits of additional information to reduce the risk of erroneous decisions and the cost of collecting this information. A method is suggested that combines existing procedures for inverse probabilistic groundwater modelling with a novel method for VOIA. The method results in (1) a prior analysis where uncertainties regarding the efficiency of safety measures are estimated, and (2) a pre-posterior analysis, where the benefits of expected uncertainty reduction deriving from additional information are compared with the costs for obtaining this information. In comparison with existing approaches for VOIA, the method can assess multiple design alternatives, use hydrogeological parameters as proxies for failure, and produce spatially distributed VOIA maps. The method is demonstrated for a case study of a planned tunnel in Stockholm, Sweden, where additional investigations produce a low number of benefits as a result of low failure rates for the studied alternatives and a cause-effect chain where the resulting failure probability is more dependent on interactions within the whole system rather than on specific features.
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| 3. |
- Sundell, Jonas, 1984, et al.
(författare)
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Comprehensive risk assessment of groundwater drawdown induced subsidence
- 2019
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Ingår i: Stochastic Environmental Research and Risk Assessment. - : Springer Science and Business Media LLC. - 1436-3240 .- 1436-3259. ; 33:2, s. 427-449
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Tidskriftsartikel (refereegranskat)abstract
- © 2019, The Author(s). We present a method for risk assessment of groundwater drawdown induced land subsidence when planning for sub-surface infrastructure. Since groundwater drawdown and related subsidence can occur at large distances from the points of inflow, the large spatial extent often implies heterogeneous geological conditions that cannot be described in complete detail. This calls for estimation of uncertainties in all components of the cause-effect chain with probabilistic methods. In this study, we couple four probabilistic methods into a comprehensive model for economic risk quantification: a geostatistical soil-stratification model, an inverse calibrated groundwater model, an elasto-plastic subsidence model, and a model describing the resulting damages and costs on individual buildings and constructions. Groundwater head measurements, hydraulic tests, statistical analyses of stratification and soil properties and an inventory of buildings are inputs to the models. In the coupled method, different design alternatives for risk reduction measures are evaluated. Integration of probabilities and damage costs result in an economic risk estimate for each alternative. Compared with the risk for a reference alternative, the best prior alternative is identified as the alternative with the highest expected net benefit. The results include spatial probabilistic risk estimates for each alternative where areas with significant risk are distinguished from low-risk areas. The efficiency and usefulness of this modelling approach as a tool for communication to stakeholders, decision support for prioritization of risk reducing measures, and identification of the need for further investigations and monitoring are demonstrated with a case study of a planned railway tunnel in Varberg, Sweden.
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| 4. |
- Garmabaki, Amir H. Soleimani, et al.
(författare)
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A Survey on Underground Pipelines and Railway Infrastructure at Cross-Sections
- 2019
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Ingår i: Proceedings of the 29th European Safety and Reliability Conference (ESREL 2019). - Singapore : Research Publishing Services. ; , s. 1094-1101
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Konferensbidrag (refereegranskat)abstract
- Underground pipelines are an essential part of the transportation infrastructure. The structural deterioration of pipelines crossing railways and their subsequent failures are critical for society and industry resulting in direct and indirect costs for all the related stakeholders. Pipeline failures are complex processes, which are affected by many factors, both static (e.g., pipe material, size, age, and soil type) and dynamic (e.g., traffic load, pressure zone changes, and environmental impacts). These failures have serious impacts on public due to safety, disruption of traffic, inconvenience to society, environmental impacts and shortage of resources. Therefore, continuous and accurate condition assessment is critical for the effective management and maintenance of pipeline networks within transportation infrastructure. The aim of this study is to identify failure modes and consequences related to the crossing of pipelines in railway corridors. Expert opinion have been collected through two set of questionnaires which have been distributed to the 291 municipalities in the whole Sweden. The failure analysis revealed that pipe deformation has higher impact followed by pipe rupture at cross-section with railway infrastructure. For underground pipeline under railway infrastructure, aging and external load gets higher ranks among different potential failure causes to the pipeline.
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| 5. |
- Mathern, Alexandre, 1986, et al.
(författare)
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Concrete Support Structures for Offshore Wind Turbines: Current Status, Challenges, and Future Trends
- 2021
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 14:7
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Forskningsöversikt (refereegranskat)abstract
- Today’s offshore wind turbine support structures market is largely dominated by steel structures, since steel monopiles account for the vast majority of installations in the last decade and new types of multi-leg steel structures have been developed in recent years. However, as wind turbines become bigger, and potential sites for offshore wind farms are located in ever deeper waters and ever further from the shore, the conditions for the design, transport, and installation of support structures are changing. In light of these facts, this paper identifies and categorizes the challenges and future trends related to the use of concrete for support structures of future offshore wind projects. To do so, recent advances and technologies still under development for both bottom-fixed and floating concrete support structures have been reviewed. It was found that these new developments meet the challenges associated with the use of concrete support structures, as they will allow the production costs to be lowered and transport and installation to be facilitated. New technologies for concrete support structures used at medium and great water depths are also being developed and are expected to become more common in future offshore wind installations. Therefore, the new developments identified in this paper show the likelihood of an increase in the use of concrete support structures in future offshore wind farms. These developments also indicate that the complexity of future support structures will increase due to the development of hybrid structures combining steel and concrete. These evolutions call for new knowledge and technical know-how in order to allow reliable structures to be built and risk-free offshore installation to be executed.
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| 6. |
- van Eldert, Jeroen, 1987-, et al.
(författare)
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Application of Measurement While Drilling Technology to Predict Rock Mass Quality and Rock Support for Tunnelling
- 2020
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Ingår i: Rock Mechanics and Rock Engineering. - : Springer. - 0723-2632 .- 1434-453X. ; 53:3, s. 1349-1358
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Tidskriftsartikel (refereegranskat)abstract
- A tunnelling project is normally initiated with a site investigation to determine the in situ rock mass conditions and to generate the basis for the tunnel design and rock support. However, since site investigations often are based on limited information (surface mapping, geophysical profiles, few bore holes, etc.), the estimation of the rock mass conditions may contain inaccuracies, resulting in underestimating the required rock support. The study hypothesised that these inaccuracies could be reduced using Measurement While Drilling (MWD) technology to assist in the decision-making process. A case study of two tunnels in the Stockholm bypass found the rock mass quality was severely overestimated by the site investigation; more than 45% of the investigated sections had a lower rock mass quality than expected. MWD data were recorded in 25 m grout holes and 6 m blast holes. The MWD data were normalised so that the long grout holes with larger hole diameters and the shorter blast holes with smaller hole diameters gave similar results. With normalised MWD data, it was possible to mimic the tunnel contour mapping; results showed good correlation with mapped Q-value and installed rock support. MWD technology can improve the accuracy of forecasting the rock mass ahead of the face. It can bridge the information gap between the early, somewhat uncertain geotechnical site investigation and the geological mapping done after excavation to optimise rock support.
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| 7. |
- Talebiahooie, Elahe, et al.
(författare)
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Modelling of Railway Sleeper Settlement under Cyclic Loading Using a Hysteretic Ballast Contact Model
- 2021
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Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 13:21
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Tidskriftsartikel (refereegranskat)abstract
- Ballasted tracks are common in the railway system as a means of providing the necessary support for the sleepers and the rails. To keep them operational, tamping and other maintenance actions are performed based on track geometry measurements. Ballast particle rearrangement, which is caused by train load, is one of the most important factors leading to track degradation. As a result, when planning maintenance, it is vital to predict the behaviour of the ballast under cyclic loading. Since ballast is a granular matter with a nonlinear and discontinuous mechanical behaviour, the discrete element method (DEM) was used in this paper to model the ballast particle rearrangement under cyclic loading. We studied the performance of linear and nonlinear models in simulating the settlement of the sleeper, the lateral deformation of the ballast shoulder and the porosity changes under the sleeper. The models were evaluated based on their ability to mimic the ballast degradation pattern in vertical and lateral direction. The linear contact model and the hysteretic contact model were used in the simulations, and the effect of the friction coefficient and different damping models on the simulations was assessed. An outcome of this study was that a nonlinear model was proposed in which both the linear and the hysteretic contact models are combined. The simulation of the sleeper settlement and the changes in the porosity under the sleeper improved in the proposed nonlinear model, while the computation time required for the proposed model decreased compared to that required for the linear model.
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| 8. |
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| 9. |
- Eitzenberger, Andreas
(författare)
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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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| 10. |
- Eitzenberger, Andreas, et al.
(författare)
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Numerical simulation of train-induced vibrations in rock masses
- 2012
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Ingår i: Harmonising rock engineering and the environment. - Leiden : CRC Press/Balkema. - 9780415804448 ; , s. 1189-1194
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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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