Norwegian Geotechnical Institute (NGI) Digital Archive
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Structural characterization and across-fault seal assessment of the Aurora CO<inf>2</inf> storage site, northern North Sea
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Sorption and Mobility of Charged Organic Compounds: How to Confront and Overcome Limitations in Their Assessment
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The use of the GIBV method for monitoring the effects of urban excavations on built heritage
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Annual Report 2021
Get PDFDuring the second year of the project period 2020-2022 of NGIs research project on snow avalanches, Applied Avalanche Research in Norway (AARN), work was conducted in all three work packages (WP 1 – Avalanche formation and release, WP 2 – Avalanche dynamics, WP 3 – Avalanche interaction) and several cross-package topics. The successful avalanche experiment in April 2021 has given us valuable insight into the dynamics of a large avalanche event and showed that the Ryggfonn test site produces the avalanches that are needed for the AARN research. During 2021, the results of the research activities have been published in peer-reviewed journals, summarised in technical notes, and presented online at national and international conferences and seminars. AARN personnel have been actively engaged in educational outreach activities, including as lecturers and student supervisors.NVE (Norges vassdrags- og energidirektorat
Deliverable 1.2 Lithology Assessment & Constitutive Model
No full textThis report focuses on assessments of lithological impact to present day in-situ stress state and integrating observations into constitutive models for application in subsequent tasks (WP1.3 and 1.4). This work is closely linked to WP3.2, and both reports seek to investigate the relative contribution of various processes (initial deposition and mineralogy, burial history including diagenesis, erosion, uplift and glacial loading) to the current in-situ stress in the North Sea basins. The content of the report includes exhumation studies using logs from DISCOS database in combination with lithology-dependent (rheological) compaction and uplift behaviour extracted from the NGI's database of soils and rocks, supplemented by rock mechanical data shared by the storage site operators. This report integrates the experimental laboratory results and empirical relationships from WP3.2 (report DV3.2), with the load history from glacial loading and burial/uplift using stress indicators from geotechnical site investigations and exhumation analysis of logs respectively. Publicly available extended leak-off tests (XLOT) and leak-off tests (LOT) complemented by additional XLOT data provided by Equinor and are used for comparison of empirical relationships defining the impact of mineralogy and burial and loading history on present day stress. We demonstrate how empirical relationships, logs and LOP data can provide useful additional insights into depth dependent and potentially lateral variations of stress within a basin, i.e. between fault blocks or CCS injection sites, and specifically in uplifted areas. Key laboratory data in report DV3.2 are brought into constitutive models to provide the link between the inferred stress history (imposed load/deformation) and the resultant stresses. A proprietary constitutive model has been applied and calibrated with laboratory datasets, which has been shown to satisfactorily capture the experimental response of various soils and soft rocks. This model calibration work is partly reported in DV1.1b, and the model is further tested and calibrated to field stress observations in this report. Workflows to assess stress from reginal trendlines in combination with a method for impact of lithology and burial history have been established and demonstrated for the SHARP CCS sites, with main focus on Aurora and Smeaheia in the Horda Platform area, and the Lisa Structure in Denmark.European CommissionpublishedVersio
Sørpeskred. Egenskaper, historikk og sikringsløsninger
Get PDFSørpeskred er en skredtype som gjør stor skade på infrastruktur og bebyggelse, men som er forsket på og dokumentert i mye mindre omfang enn for eksempel snøskred og flomskred. Sørpeskred oppstår når snødekket mettes med vann og mobiliseres som en flytende masse nedover skredløpet. Det pågår diskusjoner om varmere vær med flere innslag av intensivt regn på snødekket om vinteren kan gi opphav til flere sørpeskred. Det er derfor viktig å kunne identifisere mulige sørpeskredområder og vurdere teknikker og konsepter for sikring mot sørpeskred. Rapporten gir en kort innføring i sørpeskred som naturfare, og hvilke prosesser som fører til sørpeskred. På bakgrunn av denne informasjonen blir ulike sikringsløsninger presentert og diskutert
Shear Strength of Soft Clay in Terms of Effective Stresses
Get PDFIt is commonly understood and accepted today that soft, contractant soils, when sheared under undrained conditions, develop high pore pressures that result in failure at a critical shear stress, occurring before the soil has been able to fully mobilize its effective stress strength parameters. This has led to the conclusion that in this type of clay, stability analyses, even for natural slopes, should be based on undrained, active and passive triaxial or plane strain strengths and possibly direct simple shear strength (Bjerrum, 1973; Ladd and Foott, 1974). The present study included an analysis of the results from undrained shear strength tests on high quality samples, and aimed at developing an expression for the undrained shear strength and "critical" shear stress as functions of effective stresses. The study demonstrates the importance of considering the effect of shear deformations, the contribution of friction and attraction to undrained strength, and how undrained shear strength is a unique result of the consolidation history of the clay. A procedure is proposed to express the undrained shear strengths measured in active and passive triaxial tests and in direct simple shear tests as functions of the effective stresses and a set of generally valid effective stress strength parameters. The framework also provides a new explanation of the notion of attraction (and cohesion) in soft clays). The study demonstrates how a set of effective stress paths from an active and a passive triaxial test can be used together to establish the consolidation conditions and to determine the effective stress strength parameters, friction angle and attraction. Using tests on clays with plasticity between 5 and 90%, the new framework provides a clear, simple and logical relationship, with decreasing friction angle and increasing attraction with increasing plasticity
