Norwegian Geotechnical Institute (NGI) Digital Archive
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The 2017 rigopiano avalanche—dynamics inferred from field observations
Get PDFThis note first summarizes the history of the manuscript “On a Continuum Model for Avalanche Flow and Its Simplified Variants” by Grigorian and Ostroumov—published in this Special Issue—since the early 1990s and explains the guiding principles in editing it for publication. The changes are then detailed and some explanatory notes given for the benefit of readers who are not familiar with the early Russian work on snow avalanche dynamics. Finally, the editor’s personal views as to why he still considers this paper of relevance for avalanche dynamics research today are presented in brief essays on key aspects of the paper, namely the role of simple and complex models in avalanche research and mitigation work, the status and possible applications of Grigorian’s stress-limited friction law, and non-monotonicity of the dynamics of the Grigorian–Ostroumov model in the friction coefficient. A comparison of the erosion model proposed by those authors with two other models suggests to enhance it with an additional equation for the balance of tangential momentum across the shock front. A preliminary analysis indicates that continuous scouring entrainment is possible only in a restricted parameter range and that there is a second erosion regime with delayed entrainment.publishedVersio
Annual Report 2019 [SP4 FoU Snøskred]
No full textNGI has conducted research on avalanches and related processes since 1973. This report gives a short insight in the work done in 2019. While experiments with artificial release of avalanches in the Ryggfonn experimental site were not possible, data was collected on natural avalanche events, both at Ryggfonn and other naturally released avalanches. Work has been done on the statistical approach on avalanche release and runout probability. The feasibility of Voellmy-based numerical models was tested against observed data and simple block models. A three-dimensional CFD model was tested to study the usefulness of detailed physically based wind fields in complex terrain for avalanche mapping and forecasting purposes. The work was presented at several meetings, papers and NGI technical notes which will be made accessible at the project webpage. Taking the results and open questions as well as external input from collaborators and stakeholders into account, the project description for 2020–2022 was elaborated for a successful continuation of the avalanche research.NVE (Norges vassdrags- og energidirektorat
Research Plan 2020–2022
Get PDFSnow avalanches are a significant natural hazard and common phenomenon in Norway. Each year, avalanches result in fatalities, evacuations, and interruptions or damage to infrastructure networks such as roads, railways, and electrical transmission lines. Persistent avalanche hazard in steep terrain is a major factor considered during land-use planning and development. During the snow season, daily or weekly variations in the avalanche danger identified in regional and applied bulletins influence the operation of transportation networks. Applied research on avalanches and their societal impacts has been conducted at the Norwegian Geotechnical Institute (NGI) since 1973. This research has been funded in part by an annual grant from the Norwegian parliament, administered by the Norwegian Water Resources and Energy Directorate (NVE – Norges vassdrags- og energi-direktorat). Recent research activities have improved our understanding of avalanche formation, movement, and impacts. Enhanced knowledge of the individual processes leading to avalanche initiation, avalanche dynamics, and avalanche impacts has been applied to developing tools to help predict avalanche occurrence, runout distance, and impact pressures. While much has been accomplished within the avalanche research community in recent years, many key questions remain. This project plan: (1) presents the research goals for the 2020-2022 period, (2) outlines the projects organization – including potential for external collaboration, and (3) presents the work-package structure and specific research tasks to be undertaken by the applied avalanche research group at NGI over the next three years.NVE (Norges vassdrags- og energidirektorat
Monitoring of displacements in the Åknes rock slope
No full textNorges vassdrags- og energidirektorat (NVE
Factual Report - Permafrost Research Site
Get PDFTwo benchmark sites are established near Longyearbyen, Svalbard (78°13’N, 15°28’E) for long-term geotechnical testing and evaluation of field investigation methods in perennially frozen soils (i.e. permafrost). These sites, named “Adventdalen” and “UNIS East” based on their location, form part the research infrastructure of the Norwegian GeoTest Sites (NGTS) project. Since 2016, efforts have focused on characterization and instrumentation of the upper 30 m of the soil stratigraphy. This report contains all results from field and laboratory tests related to the NGTS permafrost site available as of the revision date. In situ methods include core drilling, electrical resistivity tomography (ERT), piezocone penetration testing (CPT), and monitoring of the ground thermal regime. Laboratory investigations include index, thermal characteristics, and unconfined compression testing.
Characterization of the Svalbard permafrost sites are summarized in two reports: (1) a factual report (20160154-06-R) and (2) an interpretation report (20160154-07-R). This report, 20160154-06-R, presents a factual summary of laboratory and in situ testing conducted at the sites in the 2016-2018 period. Site specific tests and methods are described in the present report. Standard methods for laboratory and in situ tests that apply for all NGTS sites are detailed in the general reports NGTS Report 02 (20160154-02-R) and NGTS Report 03 (20160154-03-R), respectively.publishedVersio
Evaluation and Monitoring of Slope Stability in Cold Region: Case Study of Man-Made Slope at Øysand, Norway
Get PDFRecently, the road and railways infrastructure developments in Norway have led to renewed interests on the geotechnical challenges associated with slope stability under freezing-thawing cycles. Despite the amount of research available on the topic, there are few comprehensive studies involving laboratory testing, numerical analysis, and field monitoring of a slope during a freezing–thawing. In this case study, a critical slope was identified in a cold region based on field and laboratory tests, and a series of numerical simulations were carried out to evaluate the governing factor of slope stability using finite element methods. A remote monitoring system was installed on a real scale man-made slope to observe its behavior against the governing factors of slope stability. As a result, it was found that slope stability at the critical slope was significantly impacted by the freezing–thawing action, which was confirmed by the initial field observations from 2019 to 2020. Later, continuous monitoring data could be used to update soil parameters and to implement an early warning system for the high risky slope areas effected by freezing–thawing action in many cold regions.publishedVersio
Algorithms for intelligent prediction of landslide displacements
Get PDFLandslides represent major threats to life and property in many areas of the world, such as the landslides in the Three Gorges Dam area in mainland China. To better prepare for landslides in this area, we explored how several machine learning algorithms (long short term memory (LSTM), random forest (RF), and gated recurrent unit (GRU)) might predict ground displacements under three types of landslides, each with distinct step-wise displacement characteristics. Landslide displacements are described with trend and periodic analyses and the predictions with each algorithm, validated with observations from the Three Gorges Dam reservoir over a one-year period. Results demonstrated that deep machine learning algorithms can be valuable tools for predicting landslide displacements, with the LSTM and GRU algorithms providing the most encouraging results. We recommend using these algorithms to predict landslide displacement of step-wise type landslides in the Three Gorges Dam area. Predictive models with similar reliability should gradually become a component when implementing early warning systems to reduce landslide risk.publishedVersio
The correlation between pO2 and pCO2 as a chemical marker for detection of offshore CO2 leakage
Get PDFA controlled CO2 release experiment was carried out in order to mimic unintended leakage of geologically stored CO2, and to study methods for detecting these leak events. The experiment was carried out at 60 m depth in the Oslo Fjord over the course of one month. During the simulated leak events, the water chemistry was monitored by sensors mounted on stationary templates located 10 and 22 m horizontally from the source, as well as sensors mounted on an Autonomous Underwater Vehicle (AUV). During baseline conditions (no CO2 release), we observe a strong biogenic correlation between O2 and CO2. This correlation is lacking during CO2 releases, indicating that the CO2-O2 correlation can be used as a marker for CO2 leakage. The same deviations were not initially detected by the CO2 sensor mounted on the AUV due to the longer response time of membrane-based CO2 sensors. However, by applying response time correction in the post-processing of the AUV CO2 data, the generated CO2 plume was detected. Moreover, the plume was clearly detected by the AUV using the faster responding pH sensors, where the correlation with O2 again could be used to confirm the anomaly.publishedVersio
Wetting-induced collapse behaviour of a natural and vegetated coarse pyroclastic soil
Get PDFUnsaturated pyroclastic soils originated by Vesuvius volcano show a collapsible behaviour upon wetting with a significant reduction in volume and rearrangement of solid skeleton. The paper investigates the role played by vegetation on wetting-induced collapse behaviour (namely, collapsibility) of reconstituted unsaturated soil specimens through two series of wetting tests in a standard oedometer. The first series of tests was performed on bare soil specimens, as to resemble the site conditions. The second group of tests was conducted on the same soil previously vegetated for 20 weeks with perennial graminae species, which are frequently used as a nature-based solution for contrasting surface erosion along slopes in different geo-environmental contexts. First, an initial small vertical net stress was applied on partially saturated specimens having similar initial saturation degree, then collapse was induced by flooding the specimens with distilled water and final vertical displacements were measured. As main outcome, soil porosity is highly reduced by the growth of grass roots. Consequently, the potential wetting collapse in the rooted soils is inhibited by low values of porosity. For similar initial soil porosity, in both bare and vegetated specimens (after root growth), a further reduction of the volumetric collapse magnitude is observed.publishedVersio