Norwegian Geotechnical Institute (NGI) Digital Archive
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Monopile responses to monotonic and cyclic loading in undrained sand using 3D FE with SANISAND-MSu
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Avalanche observations versus numerical avalanche model: Simple test of model performance
Get PDFHazard assessment for landuse planning in snow avalanche prone areas requires, besides knowledge of return periods, the specification of expected runout distances. For a complete risk assessment, additionally, the intensity of the event, often expressed in terms of impact pressures, and the corresponding vulnerability of endangered objects are needed.
To obtain dynamical parameters, such as velocity, it has become state of practice to use 2-dimensional depth integrated avalanche models like RAMMS (Christen et al. 2010) or SAMOS-AT (Sampl and Granig, 2009). However, those models still lack a thorough and documented validation - which is partly caused by the lack of sufficient avalanche
data - and therefore, it requires extensive experience from practitioners to assess the model results. Mainly, the models are calibrated based on runout observation, however runout observations provide limited constraints for the validation of the empirical parameters used in common present-day numerical avalanche models. On the other hand side, observations of runout distances combined with velocity meas urements suggest that "major'' dry-mixed avalanches show a scale invariance to the total drop height HSC. This is in accordance to the proposed upper-limit envelope of the maximum velocity by McClung and Schaerer (2003) and a simple scaling analysis using a simple mass block model on cycloidal and parabolic tracks (Gauer, 2018). Therefore, those combined observations give a much more stringent constrain for the parameter choice.NVE (Norges vassdrags- og energidirektorat
CTBT seismic monitoring using coherent and incoherent array processing
Get PDFThe detection and location capability of the International Monitoring System for small seismic events in the continental and oceanic regions surrounding the Sea of Japan is determined mainly by three primary seismic arrays: USRK, KSRS, and MJAR. Body wave arrivals are coherent on USRK and KSRS up to frequencies of around 4 Hz and classical array processing methods can detect and extract features for most regional signals on these stations. We demonstrate how empirical matched field processing (EMFP), a generalization of frequency-wavenumber or f-k analysis, can contribute to calibrated direction estimates which mitigate bias resulting from near-station geological structure. It does this by comparing the narrowband phase shifts between the signals on different sensors, observed at a given time, with corresponding measurements on signals from historical seismic events. The EMFP detection statistic is usually evaluated as a function of source location rather than slowness space and the size of the geographical footprint valid for EMFP templates is affected by array geometry, the available signal bandwidth, and Earth structure over the propagation path. The MJAR array has similar dimensions to KSRS but is sited in far more complex geology which results in poor parameter estimates with classical f-k analysis for all signals lacking energy at 1 Hz or below. EMFP mitigates the signal incoherence to some degree but the geographical footprint valid for a given matched field template on MJAR is very small. Spectrogram beamforming provides a robust detection algorithm for high-frequency signals at MJAR. The array aperture is large enough that f-k analysis performed on continuous AR-AIC functions, calculated from optimally bandpass-filtered signals at the different sites, can provide robust slowness estimates for regional P-waves. Given a significantly higher SNR for regional S-phases on the horizontal components of the 3-component site of MJAR, we would expect incoherent detection and estimation of S-phases to improve with 3-component sensors at all sites. Given the diversity of the IMS stations, and the diversity of the methods which provide optimal results for a given station, we advocate the development of seismic processing pipelines which can process highly heterogeneous inputs to help associate characteristics of the incoming signals with physical events.publishedVersio
Legacy and emerging organohalogenated compounds in feathers of Eurasian eagle-owls (Bubo bubo) in Norway: Spatiotemporal variations and associations with dietary proxies (δ13C and δ15N)
Get PDFThe occurrence of organohalogenated compounds (OHCs) in wildlife has received considerable attention over the last decades. Among the matrices used for OHCs biomonitoring, feathers are particularly useful as they can be collected in a minimally or non-invasive manner. In this study, concentrations of various legacy OHCs –polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs)–, as well as emerging OHCs –per- and polyfluoroalkyl substances (PFAS) and organophosphate ester flame retardants (OPEs)– were determined in feathers of 72 Eurasian eagle-owls (Bubo bubo) from Norway, with the goal of studying spatiotemporal variation using a non-invasive approach. Molted feathers were collected at nest sites from northern, central and southern Norway across four summers (2013–2016). Additionally, two museum-archived feathers from 1979 to 1989 were included. Stable carbon (δ13C) and nitrogen isotopes (δ15N) were used as dietary proxies. In total, 11 PFAS (sum range 8.25–215.90 ng g− 1), 15 PCBs (4.19–430.01 ng g− 1), 6 OCPs (1.48–220.94 ng g− 1), 5 PBDEs (0.21–5.32 ng g− 1) and 3 OPEs (4.49–222.21 ng g− 1) were quantified. While we observed large variation in the values of both stable isotopes, suggesting a diverse diet of the eagle owls, only δ13C seemed to explain variation in PFAS concentrations. Geographic area and year were influential factors for δ15N and δ13C. Considerable spatial variation was observed in PFAS levels, with the southern area showing higher levels compared to northern and central Norway. For the rest of OHCs, we observed between-year variations; sum concentrations of PCBs, OCPs, PBDEs and OPEs reached a maximum in 2015 and 2016. Concentrations from 1979 to 1989 were within the ranges observed between 2013 and 2016. Overall, our data indicate high levels of legacy and emerging OHCs in a top predator in Norway, further highlighting the risk posed by OHCs to wildlife. Keywords: Bird of prey Feathers Isotopes OPE POP PFASpublishedVersio
Excavated vs novel in situ soil washing as a remediation strategy for sandy soils impacted with per- and polyfluoroalkyl substances from aqueous film forming foams
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Multiphase Navier–Stokes Equations applied to landslide tsunamis : Numerical simulations of granular flows and their interaction with water bodies
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ACT4storage - Acoustic and Chemical Technologies for environmental monitoring of geological carbon storage. D3 - Nearshore evaluation report 2019
Get PDFThis report is the second delivery of the CLIMIT demonstration project ACT4storage
(Acoustic and Chemical Technologies for environmental monitoring of geological
carbon storage). The ACT4storage project is funded by Gassnova and Industry Partners.
During this project, we have conducted a series of controlled CO2 release experiments
to assess the performance of different sensor technologies in different environments. In
2018 we conducted laboratory tests over several weeks to evaluate the capabilities of
relevant chemical sensors in a controlled environment. In the fall of 2018 we conducted
an 8-week long field trial in a sheltered area of the Oslo fjord to further study the
capabilities and limitations of chemical as well as acoustic sensors in a more realistic
environment. This report describes the second and final round of nearshore controlled
release experiments conducted in the spring of 2019, also in the Oslo fjord but in deeper
water and ocean conditions similar to the North Sea environment. ...publishedVersio
Variability in the three-dimensional geometry of segmented normal fault surfaces
Get PDFNormal faults are often complex three-dimensional structures comprising multiple sub-parallel segments separated by intact or breached relay zones. Relay zones are classified according to whether they step in the strike or dip direction and whether the relay zone-bounding fault segments are unconnected in 3D or bifurcate from a single surface. Complex fault surface geometry is described in terms of the relative numbers of different types of relay zones to allow comparison of fault geometry between different faults and different geological settings. A large database of fault surfaces compiled primarily from mapping 3D seismic reflection surveys and classified according to this scheme, reveals the diversity of 3D fault geometry. Analysis demonstrates that mapped fault geometries depend on geological controls, primarily the heterogeneity of the faulted sequence and the presence of a pre-existing structure, as well as on resolution limits and biases in fault mapping from seismic data. Where a significant number of relay zones are mapped on a single fault, a wide variety of relay zone geometries occurs, demonstrating that individual faults can comprise segments that are both bifurcating and unconnected in three dimensions.Variability in the three-dimensional geometry of segmented normal fault surfacespublishedVersio
Quick-clay landslide mitigation using potassium-chloride wells: Installation procedures and effects
Get PDFMitigation actions related to quick-clay slopes often induce undesirable changes to the terrain that may have negative impact on developed areas and local biodiversity. Soil improvement may prevent this. Lime-cement piling causes temporarily reduced slope stability and substantial climate-gas emissions. Less climate-gas emissions are associated to the production of potassium chloride (KCl). KCl improves the post-failure properties of quick clay so it renders not quick and may serve as an alternative to current landslide-mitigation. The mechanisms in this chemical process is well documented, but there exist no installation procedures for KCl wells, nor knowledge on cost/benefit or climate-gas emissions. This paper presents two installation procedures of KCl wells, and studies showing that the climate-gas emissions are far less than installing lime-cement piles. Further development of cost-effective installation procedures is needed to justify application of KCl wells in quick-clay areas.publishedVersio