Norwegian Geotechnical Institute (NGI) Digital Archive
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WP1 - Temporary storage of black shales – a compilation of case studies, experiences and overall conclusions
Get PDFAs a part of the internal R&D project "Under Oslo" at NGI, several aspects of temporary storage of black shale has been investigated. Information from different experiments and cases of black shale storage from the Cambro-Ordovician stratigraphy in the Oslo area have been gathered.
For the large scale, outdoor experiments with fresh black shale, minimum 14 months was necessary for acid rock drainage (ARD) to start. This is because the black shales have an inherent buffer capacity in the form of carbonates that buffers the acid and cannot be expected for already weathered shale where part of the buffer capacity may have been consumed. For small-scale column experiment at room temperature, the pH dropped after about 10 months.
Two cases of self-heating in alum shale are described. In both cases, the time until significant self-heating was more than a year. Factors affecting this probability will likely be reactivity of the rock masses (e.g. content of sulphides and neutralizing material), size distribution and porosity of the rock masses, storage conditions including height of pile, moisture and air circulation in the pile. Covering masses with tarpaulin can both increase and reduce the risk of self-heating.
One stage batch leaching tests are not appropriate for assessing the acid-producing properties of black shale, but may give information about the degree of weathering of the material. However, even by ongoing ARD, crushing the material can release carbonates resulting in neutral pH.
Downstream water quality of three sites with neutral leaching from black shale is presented and are mainly within environmental guideline values. Some elevated uranium values were however observed. Tests with different basic materials for neutralizing ARD gives varying results, showing the need for testing materials before use.
Based on the results of all these findings, a maximum of 6 months temporary storage before final disposal of acid producing black shales is recommended. This time period includes temporary storage at the disposal sites before the masses are properly covered.Norges forskningsrå
A Framework for Mooring and Anchor Design in Sand Considering Seabed Trenches Based on Floater Hydrodynamics
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Characterizing along- and across-fault fluid-flow properties for assessing flow rates and overburden fluid migration along faults: a case study from the North Sea
Get PDFAssessing fault zones as fluid-migration pathways requires the characterization of permeability both across and along faults, as well as the adjacent volume. The hydraulic properties of the Vette Fault Zone, North Sea, are described by modelling the mixing of host-rock lithologies into the fault zone, and the fault width is derived from empirical relationships as a function of throw and clay content. To better understand the sensitivity related to the uncertainties in overburden lithologies and fault-width correlations, a parametric study with 1125 model realizations were solved in a 2D steady-state, single-phase, subsurface flow model. The fault zone, included as a discrete permeable structure, significantly alters the flow field compared to a model that only considers lithological juxtaposition. The most prominent hydraulic communication in the Vette Fault Zone is downwards from the storage reservoir where sand is mixed into the fault zone. Increasing the host-rock permeability in the overburden also increases the fault permeability and shifts the inflection point for down-fault flow, causing the pressurized reservoir to drain towards the overburden and the top surface. For CO2 storage application, the models highlighted the potential for downward communication along the fault for brine, and the CO2 capillary sealing towards the overburden.Characterizing along- and across-fault fluid-flow properties for assessing flow rates and overburden fluid migration along faults: a case study from the North SeapublishedVersio
The decomposition and emission factors of a wide range of PFAS in diverse, contaminated organic waste fractions undergoing dry pyrolysis
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Ocean-Ionosphere Disturbances Due To the 15 January 2022 Hunga-Tonga Hunga-Ha'apai Eruption
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Time series modelling: applications for groundwater control in urban tunnelling
Get PDFWater ingress to tunnels may result in pore pressure drawdown and consolidation settlements in areas above tunnels founded on soft soil deposits, potentially causing damage to buildings and infrastructure. To limit pore pressure drawdown, requirements are set on water ingress to bedrock tunnels. To meet these requirements, pre-excavation grouting is often performed to reduce the hydraulic conductivity of the rock mass surrounding the tunnel. Real-time pore pressure monitoring may be used to document pore pressure drawdown during construction. However, the effect of tunnel water ingress can be difficult to distinguish from natural pore pressure fluctuations. This paper presents a tunnel case in Oslo, Norway, where time series modelling was applied to local pore pressure data using the transfer function model framework. The input to the models was daily meteorological data considering precipitation and evapotranspiration, and the output was simulated pore pressure levels with impulse response functions. The models were optimised with data from before tunnel excavation, and simulations were run during the tunnel excavation period. Simulated pore pressure levels were compared with observed pore pressure levels to assess tunnelling-induced drawdown. Model uncertainty ranges were used to produce upper, lower, and best estimates of the drawdown. The findings show that time series modelling with transfer function models may be used in tunnel projects to continuously assess the impact on the local groundwater environment, for better evaluation of the pre-grouting performance, and for quantifying both the temporary and long-term drawdown with increased accuracy.Time series modelling: applications for groundwater control in urban tunnellingpublishedVersio
A trade-off in activated biochar capping of complex sediment contamination: reduced PAH transport at the cost of potential As mobilisation
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A multiproxy approach to understanding the impact of the Storegga tsunami upon Mesolithic hunter-fisher-gatherers across different regions of western Norway
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