| 1. |
- 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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| 2. |
- Merisalu, Johanna, 1990, et al.
(författare)
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A Framework for Risk-Based Cost-Benefit Analysis for Decision Support on Hydrogeological Risks in Underground Construction
- 2021
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Ingår i: Geosciences (Switzerland). - : MDPI AG. - 2076-3263. ; 11:2, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- Construction below the ground surface and underneath the groundwater table is often associated with groundwater leakage and drawdowns in the surroundings which subsequently can result in a wide variety of risks. To avoid groundwater drawdown-associated damages, risk-reducing measures must often be implemented. Due to the hydrogeological system's inherent variability and our incomplete knowledge of its conditions, the effects of risk-reducing measures cannot be fully known in advance and decisions must inevitably be made under uncertainty. When implementing risk-reducing measures there is always a trade-off between the measures' benefits (reduced risk) and investment costs which needs to be balanced. In this paper, we present a framework for decision support on measures to mitigate hydrogeological risks in underground construction. The framework is developed in accordance with the guidelines from the International Standardization Organization (ISO) and comprises a full risk-management framework with focus on risk analysis and risk evaluation. Cost-benefit analysis (CBA) facilitates monetization of consequences and economic evaluation of risk mitigation. The framework includes probabilistic risk estimation of the entire cause-effect chain from groundwater leakage to the consequences of damage where expert elicitation is combined with data-driven and process-based methods, allowing for continuous updating when new knowledge is obtained.
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| 3. |
- Merisalu, Johanna, 1990, et al.
(författare)
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Kostnads-nyttoanalys av skyddsåtgärder för hantering av hydrogeologiska risker vid undermarksbyggande, Fallstudie Förbifart Stockholm
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Vid byggande under marknivå och under rådande grundvattenyta kan grundvatten läcka in i anläggningen. Eftersom arbeten i anläggningen samt driften av anläggningen måste utföras i torra miljöer måste inläckande grundvatten i sådana situationer ledas bort. Om sättningskänsliga jordar finns inom påverkansområdet riskerar grundvattenbortledning att orsaka marksättningar vilka i sin tur riskerar att skada byggnader och andra anläggningar. För att reducera risken för skada kan verksamhetsutövaren vidta skyddsåtgärder. Vid genomförande av åtgärder finns det två typer av risker: 1) att inte genomföra en åtgärd som borde genomföras med skador på omgivningen som följd, och 2) att genomföra en åtgärd som inte borde genomföras med onödiga kostnader som följd. För att minska dessa två risker krävs det att åtgärders kostnader och nyttor vägs mot varandra. Det övergripande syftet med denna rapport är att presentera och exemplifiera en probabilistisk kostnads-nyttoanalys av åtgärdsalternativ för hantering av hydrogeologiska risker i undermarksprojekt genom en fallstudie för projekt Förbifart Stockholm. Det övergripande syftet nås genom att de ekonomiska konsekvenserna av marksättning till följd av grundvattensänkning beräknas samt att identifierade kostnader och nyttor av olika åtgärdsalternativ relativt ett nollalternativ jämförs. Resultatet från kostnads-nyttoanalysen visar att nyttorna i form av minskad ekonomisk skaderisk är små (ca 70 miljoner) relativt kostnaderna för att genomföra de tätningsåtgärder som krävs för att efterleva de inläckagevillkor som anges i tillståndsdomen för projektet (flera miljarder). Kostnads-nyttoanalysen exemplifierar också nyttan i att använda sig utav en strukturerad modell för att utvärdera lönsamheten hos olika åtgärdsalternativ.
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| 4. |
- Merisalu, Johanna, 1990, et al.
(författare)
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Probabilistic cost-benefit analysis for mitigating hydrogeological risks in underground construction
- 2023
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798. ; 131
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Tidskriftsartikel (refereegranskat)abstract
- Leakage of groundwater into underground facilities can subsequently cause groundwater drawdown, subsidence and subsidence damages to the built-up environment. In order to reduce the risk of damage, measures to mitigate the risks must often be implemented. The aim of this paper is to describe and demonstrate a probabilistic cost-benefit analysis approach to assess the economic profitability of investing in different risk mitigation alternatives. Since underground construction is always associated with uncertainties, the analysis uses probability distribution functions for uncertain parameters and Monte Carlo simulations to quantify probabilities of damage and implementation costs. The proposed approach is exemplified with a case study, the road tunnel project Bypass (Förbifart) Stockholm in eastern Sweden, for which four risk mitigation alternatives were evaluated. In conclusion, the approach helps to highlight the economic effects of different risk mitigation approaches and constitute a transparent support for decisions on implementation of risk mitigation. For the case study, the analysis indicates that the implementation costs of ∼ 7000 MSEK (700 million EUR) for risk mitigation needed to fulfil the legal requirements, from the Swedish Land- and Environmental court, in the form of ambitious sealing strategies are disproportionate relative to the benefits of ∼ 50 MSEK (5 million EUR) gained in the form of reduced damage risk for the built-up environment. In other words, billions SEK of taxpayers' money are spent on unnecessary expenses to fulfill legal requirements without societal benefits. The novelty of the paper constitutes the coupling of models and combination of established methods for management of hydrogeological risks.
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| 5. |
- Sundell, Jonas, 1984, et al.
(författare)
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A framework for Risk Assessment of Groundwater Drawdown Induced Subsidence
- 2015
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Ingår i: 5th International Symposium on Geotechnical Safety and Risk (ISGSR). - Amsterdam : Ios Press. - 9781614995807 ; , s. 256-262
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Konferensbidrag (refereegranskat)abstract
- Sub-surface constructions generally involve drainage of groundwater, which can induce land subsidence in compressible soil deposits and cause extensive damage costs in urban areas. A probabilistic framework, in accordance with the risk management framework outlined by the International Standard Organization (ISO), for assessing risks of groundwater drawdown induced subsidence is presented here. The framework consists of five modules: (1) A stratified geostatistical (Kriging) procedure for probabilistic spatial analysis of soil layers. This module is necessary for a detailed understanding of the soil stratification, drainage paths, and their potential spatial variations; (2) A stochastic hydrogeological model capable of representing possible groundwater drawdowns for a specific sub-surface construction; (3) A stochastic subsidence model; (4) A model for estimating the economic consequences and calculating the risk, i. e. the expected cost, of groundwater induced subsidence; and (5) A module for evaluating the need for additional information to reduce the risk of erroneous decisions with respect to risk acceptance criteria based on economic Value of Information Analysis (VOIA), i. e. a cost-benefit analysis (CBA) of additional information collection alternatives for suggested strategies to reduce or control subsidence. The modelled land-area is represented by a grid with calculation points. When the three first modules are linked together in a Monte Carlo-simulation, it is possible to estimate the spatial distribution of probability of subsidence and evaluate the sensitivity to different model and parameter assumptions. An estimation of the risk of subsidence is performed by combining the probability of land subsidence with the locations and expected damage costs of existing buildings across the modeled area (module 4). With sensitivity analysis, significant weaknesses can be identified and robust safety measures at locations with significant risks for subsidence can be planned for. Uncertainties can be communicated by mapping and comparing different outcomes of the model, e. g. the expected value and the 95th percentile of the risk. Together with affected stakeholders the assumptions and the outcomes of the model should be discussed - both how well the model describes the system dynamics and how safety measures should be implemented.
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| 6. |
- Sundell, Jonas, 1984, et al.
(författare)
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A probabilistic approach to soil layer and bedrock-level modelling for risk assessment of groundwater drawdown induced land subsidence
- 2016
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Ingår i: Engineering Geology. - : Elsevier BV. - 0013-7952. ; 203, s. 126-139
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Tidskriftsartikel (refereegranskat)abstract
- Sub-surface construction in urban areas generally involves drainage of groundwater, which can induce subsidence in soil deposits. Knowledge of where compressible sediments are located and how thick these are is essential for estimating subsidence risk. A probabilistic method for coupled bedrock-level and soil-layer modeling to detect compressible sediments is presented. The method is applied in an area in central Stockholm, where clay is the compressible sediment layer. First, a bedrock-level model was constructed from three sources of information: (a) geotechnical drillings reaching the bedrock; (b) drillings not reaching the bedrock; and (c) mapped bedrock outcrops. Input data for the probabilistic bedrock-level model was generated by a stepwise Kriging procedure. Second, a three layer soil model was constructed, including the following materials: (a) coarse grained post glacial and filling material below the ground surface; (b) glacial and post-glacial clays; and (c) coarse grained glaciofluvial and glacial till deposits above the bedrock. Layer thicknesses were transformed to proportions of the total soil thickness. Since Kriging requires data to be normally distributed, the proportions were transformed from proportions (P) to standard normal quantiles (z). In each iteration of a Monte-Carlo simulation, a spatial distribution of the bedrock level was simulated together with the transformed values for the soil-layer proportions. From the iterations, the probability density of the clay thickness (compressible sediments) at each grid cell was calculated. The results of the case study map the expected value (mean) and the 95th percentile of the probability of compressible sediments at specific locations. The resulting model is geologically realistic and validated through a cross-validation procedure in order to be in good agreement with a reference dataset. The case study showed that the method can efficiently handle large amounts of data and requires little manual adjustment. Moreover, the mapped results can provide useful decision support when planning risk-reducing measures and when communicating with stakeholders. Although this novel method is developed for risk assessment of groundwater drawdown induced subsidence, it is useful for other applications involving spatial soil strata modeling.
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| 7. |
- 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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| 8. |
- Sundell, Jonas, 1984
(författare)
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Risk Assessment of Groundwater Drawdown in Subsidence Sensitive Areas
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Groundwater leakage into sub-surface constructions can result in drawdown, subsidence in compressible materials, and costly damage to buildings and installations. When planning for sub-surface constructions where there is a risk for land subsidence due to groundwater drawdown, the need for safety measures must be carefully evaluated and managed. Since the sub-surface consists of heterogeneous and anisotropic materials, which cannot be fully investigated in all aspects, decisions regarding safety measures must be taken under uncertainty. In this thesis, a generic framework is presented on how to assess the risk of groundwater drawdown-induced subsidence (Paper I). As specific tools for modelling uncertainties in the groundwater drawdown – subsidence – damage chain, a method for probabilistic modelling of bedrock levels and soil stratification (Paper II) and a method for probabilistic modelling of ground subsidence to a large spatial extent (Paper III) are presented. These are combined with a probabilistic groundwater model and cost functions to calculate the economic risks of subsidence damage between different design alternatives (Paper IV). Finally, a novel method for economic valuation of hydrogeological information is presented in Paper V. The methods presented can distinguish between low and high-risk areas, identify the alternative with the highest net benefit compared to a reference alternative, and estimate the expected benefit of additional information. The methods have been demonstrated to provide useful support for decision-making and communication tools when assessing the risk of large-scale groundwater drawdown-induced subsidence in different infrastructure projects in Sweden.
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| 9. |
- Sundell, Jonas, 1984
(författare)
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Risk Estimation of Groundwater Drawdown in Subsidence Sensitive Areas
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Groundwater drawdown induced ground subsidence is a severe problem in many regions around the world. Leakage of groundwater into a sub-surface construction, resulting in drawdown and subsequent subsidence, can lead to immense damage costs on buildings and installations in urban areas. To reduce the risk for damages safety measures can be implemented. Safety measures include design change of the construction, sealing of fractures in bedrock and permeable formations in soil, and infiltration of water to maintain stable groundwater heads. However, such measures can be very expensive and extensive investigation programs are therefore commonly realized as a basis for decision support on the need for safety measures. Since the sub-surface consists of heterogeneous and anisotropic materials which cannot be investigated in its entirety, decisions on safety measures have to be taken under uncertainty. In this thesis, a generic framework is presented on how to assess the risk for groundwater drawdown induced subsidence (Paper I). As specific tools for modelling uncertainties in the groundwater drawdown – subsidence – damage chain, a method for probabilistic modelling of bedrock levels and soil stratification (Paper II) and a method for probabilistic modelling of ground subsidence at the city scale (Paper III) are presented.
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| 10. |
- Sundell, Jonas, 1984, et al.
(författare)
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Risk Mapping of Groundwater-Drawdown-Induced Land Subsidence in Heterogeneous Soils on Large Areas
- 2019
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Ingår i: Risk Analysis. - : Wiley. - 0272-4332 .- 1539-6924. ; 39:1, s. 105-124
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Tidskriftsartikel (refereegranskat)abstract
- Groundwater leakage into subsurface constructions can cause reduction of pore pressure and subsidence in clay deposits, even at large distances from the location of the construction. The potential cost of damage is substantial, particularly in urban areas. The large-scale process also implies heterogeneous soil conditions that cannot be described in complete detail, which causes a need for estimating uncertainty of subsidence with probabilistic methods. In this study, the risk for subsidence is estimated by coupling two probabilistic models, a geostatistics-based soil stratification model with a subsidence model. Statistical analyses of stratification and soil properties are inputs into the models. The results include spatially explicit probabilistic estimates of subsidence magnitude and sensitivities of included model parameters. From these, areas with significant risk for subsidence are distinguished from low-risk areas. The efficiency and usefulness of this modeling 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 tunnel in Stockholm.
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