Norwegian Geotechnical Institute (NGI) Digital Archive
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Fluorinated Precursor Compounds in Sediments as a Source of Perfluorinated Alkyl Acids (PFAA) to Biota
Get PDFThe environmental behavior of perfluorinated alkyl acids (PFAA) and their precursors was investigated in lake Tyrifjorden, downstream a factory producing paper products coated with per- and polyfluorinated alkyl substances (PFAS). Low water concentrations (max 0.18 ng L–1 linear perfluorooctanesulfonic acid, L-PFOS) compared to biota (mean 149 μg kg–1 L-PFOS in perch livers) resulted in high bioaccumulation factors (L-PFOS BAFPerch liver: 8.05 × 105–5.14 × 106). Sediment concentrations were high, particularly for the PFOS precursor SAmPAP diester (max 1 872 μg kg–1). Biota-sediment accumulation factors (L-PFOS BSAFPerch liver: 22–559) were comparable to elsewhere, and concentrations of PFAA precursors and long chained PFAA in biota were positively correlated to the ratio of carbon isotopes (13C/12C), indicating positive correlations to dietary intake of benthic organisms. The sum fluorine from targeted analyses accounted for 54% of the extractable organic fluorine in sediment, and 9–108% in biota. This, and high trophic magnification factors (TMF, 3.7–9.3 for L-PFOS), suggests that hydrophobic precursors in sediments undergo transformation and are a main source of PFAA accumulation in top predator fish. Due to the combination of water exchange and dilution, transformation of larger hydrophobic precursors in sediments can be a source to PFAA, some of which are normally associated with uptake from water.publishedVersio
A Benchmark Case Study for Seismic Event Relative Location
Get PDF“Precision seismology” encompasses a set of methods which use differential measurements of time-delays to estimate the relative locations of earthquakes and explosions. Delay-times estimated from signal correlations often allow far more accurate estimates of one event location relative to another than is possible using classical hypocenter determination techniques. Many different algorithms and software implementations have been developed and different assumptions and procedures can often result in significant variability between different relative event location estimates. We present a Ground Truth (GT) database of 55 military surface explosions in northern Finland in 2007 that all took place within 300 meters of each other. The explosions were recorded with a high signal-to-noise ratio to distances of about 2 degrees, and the exceptional waveform similarity between the signals from the different explosions allows for accurate correlation-based time-delay measurements. With exact coordinates for the explosions, we are able to assess the fidelity of relative location estimates made using any location algorithm or implementation. Applying double-difference calculations using two different 1-d velocity models for the region results in hypocenter-to-hypocenter distances which are too short and it is clear that the wavefield leaving the source region is more complicated than predicted by the models. Using the GT event coordinates, we are able to measure the slowness vectors associated with each outgoing ray from the source region. We demonstrate that, had such corrections been available, a significant improvement in the relative location estimates would have resulted. In practice we would of course need to solve for event hypocenters and slowness corrections simultaneously, and significant work will be needed to upgrade relative location algorithms to accommodate uncertainty in the form of the outgoing wavefield. We present this dataset, together with GT coordinates, raw waveforms for all events on six regional stations, and tables of time-delay measurements, as a reference benchmark by which relative location algorithms and software can be evaluated.publishedVersio
Coupled hydro-mechanical stability analysis of Åknes rock slope
Get PDFStability of Åknes rock slide was assessed by coupled hydro-mechanical numerical analysis. The analysis was carried out by considering explicitly the rock joints network and the sliding planes.
Numerical analysis shows that with draining all the groundwater from the sliding surface the factor safety will improve ca. 0.5 and 4 % in the east and west flank of the slope, respectively.
Fast infilling of the backscarp due to flooding can destabilise the west flank: decreasing the factor of safety to 0.89.
It was shown that in hypothetically highest groundwater level inside the rock mass, the west flank has higher tendency of becoming unstable than the east flank.Norges vassdrags- og energidirektorat (NVE
A procedure for predicting the permanent rotation of monopiles in sand supporting offshore wind turbines
Get PDFFoundations for Offshore Wind Turbines (OWTs) are designed following the limit state philosophy. One of the considered states is the Serviceability Limit State (SLS), which verifies that the permanent rotation of the foundation generated from accumulated strains in the soil is below a project specific criterion. Despite design codes requiring an estimation of the permanent rotation, there is not clear guidance on how to implement this. This paper describes a methodology to estimate the monopile permanent rotation for SLS and discusses its advantages and limitations. The methodology combines an accumulation method with results from 3D Finite Element Analyses (FEA) and a soil model that accounts for strain accumulation as a function of the number of cycles, relative density and load characteristics. The performance of the proposed methodology is compared against experimental centrifuge tests and results from advanced 3D FEA, indicating that it can predict the permanent rotation with satisfactory accuracy, and with a considerable reduction in computational effort. This is important for the design of OWTs, where different load histories might be required to be checked – often under tight time constraints – to find which load history leads to the largest permanent rotation, and therefore is more critical to SLS design.publishedVersio
Interaction of deformation bands and fractures during progressive strain in monocline - San Rafael Swell, Central Utah, USA
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A multi-spring model for monopile analysis in soft clays
Get PDFThe offshore wind industry in China has seen a rapid development in recent years and is projected to account for half of global yearly installed capacity in the years to come. Monopiles are a popular foundation solution for supporting offshore wind turbines. However, due to challenging seabed soil conditions, which often feature thick normally consolidated soft clays and harsh environmental loading (i.e. frequent occurrence of typhoons), extremely long monopiles are often designed. The large monopiles are costly to fabricate and install and sometimes kills the viability of the concept in cases where the bedrock is relatively shallow and expensive piling in rock is otherwise required. However, the state-of-practice for designing these monopiles in clays is typically by using the API p-y springs, which are widely known to underestimate soil-pile interaction stiffness and capacity for large diameter monopiles. Improvement to the design method can therefore have significant economic implications to the industry. The paper presents an effort toward this direction. A multi-spring beam-column model suitable for monopile design in soil conditions in China is proposed. The model features three soil spring components, namely the lateral p-y spring, the pile tip base shear s-y spring and rotational m-θ springs along the pile shaft. The validity of the model is verified by a comprehensive suite finite element parametric analyses. Guidance for incorporating the cyclic loading effect into design is also provided. The model proposed in this paper has large potentials for application in design practice.publishedVersio
Compaction, rock physics and rock properties of sandstones of the Stø Formation: Case study of five wells from the south-western Barents Sea, Norway
Get PDFFive wells containing Lower-Middle Jurassic sandstones of Stø Formation from the Hammerfest Basin (7120/9–1, 7121/7–1), the Ringvassøy-Loppa Fault Complex (7119/12–1, 7119/12–4) and the Troms-Finnmark Fault Complex (7019/1-1) in the Barents Sea area are considered in this study. The Stø Formation sandstones contain dominantly very fine-to medium-grained quartz arenites with occasional coarse-grained sandstone layers. Feldspathic and quartz wackes are also present. The effect of compaction and exhumation on reservoir properties (porosity and permeability) and seismic property (P-wave velocity) of these sandstones have been investigated. Source of quartz cement has also been investigated. Forty polished thin sections embedded in blue epoxy were studied using optical microscopy, scanning electron microscopy and cathodoluminiscence. Bulk mineralogy was also analysed using X-ray diffraction. The studied sandstones have experienced Cenozoic exhumation ranging between 820 and 1050 m. P-wave velocity is higher; porosities and permeabilities are lower in the western wells (7019/1-1, 7119/12–1 and 7119/12–4) compared to the eastern wells (7120/9–1 and 7121/7–1). Rock physics models and diagnostics show that the western wells are diagenetically more mature, stiffer, more compacted and more cemented than the eastern wells. These trends are attributed largely to difference in burial history from the east to the west and less to textural variations. Quartz cement is the most important authigenic mineral in these sandstones. Quartz cement in the western well (7119/12–1) is predominantly derived from clay-induced dissolution at macrostylolites whereas the eastern wells (7120/9–1 and 7121/7–1) are mostly sourced from clay-induced dissolution at grain contacts or microstylolites. While cementational porosity loss dominates in the western wells, compactional porosity loss dominates in the eastern wells. Compaction can reduce porosities down to 26% and this might be the reason for better porosity preservation and reservoir quality in the eastern wells than in the western wells.publishedVersio
Dynamic Field Data from Offshore Monopile Wind Turbines - Assessment of Natural Frequencies and Damping
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Input to data report on hydraulic investigations in boreholes - from 2017 and 2018
Get PDFThis technical note is revised and include a summary of methodology and results from packer tests in 2017 and 2018 boreholes. The packer tests were performed with both single step pressure tests and 5 step pressure tests.
Packer test "Lugeon tests" were performed in borehole KH-01-2017 and KH-02-2017 in August and October/November 2017 and KH-01-2018 and KH-02-2018 in July/August and September/October 2018 (Figure 1). Testing was performed by Geodrilling.Norges vassdrags- og energidirektorat (NVE