Disputas

Background for this study 
The main challenge to the development of oil and gas industries and the exploitation of these resources in the Arctic is sea ice. Safe structures and ships should be designed taking into account sea ice concentration, thickness and strength. The ice loads modeling has progressed the past few years, but there are still some uncertainties regarding the magnitude of ice loads in structures and ships. In the absence of icebergs, ice ridges are the governing factor in Arctic marine design.  Data must be collected on ice properties (thickness as well as temperature, salinity, density and strength) for more accurate modeling. In addition, the consolidation and aging process of sea ice ridges is yet not well understood (e.g. in the Fram Strait).

The study locations were Van Mijenfjorden, Van Keulenfjorden, the Barents Sea (near Hopen) and the Fram Strait.

The PhD research was divided into two parts: the study of level ice and the study of sea ice ridges.

The level ice studies aimed at:

• Better understanding the variation of sea ice strength through and across the ice sheet and how it changes with time. An important finding was that the variability of the uniaxial compressive strength is strongly related to the localization of the brine (pockets and channels) in the sea ice.
• Establishing a statistical distribution for the uniaxial compressive strength by using more than 1000 samples, collected from 2005 to 2011.
• Studying the propagation of stresses in sea ice. The stresses were expressed as a function of the distance.

The ridges studies aimed at:

• Studying the evolution of first- and second-year ridges. It was observed that the water below the level is involved in the desalination process and that small ridges of landfast ice should erode faster in tidal currents than larger ridges
• Gathering and improving the knowledge on the morphology of first-year sea ice ridges. A very large amount of published data was collected and analyzed in what is the biggest catalogue and review on the morphological properties of first-year floating ice ridges published until now. Important correlations between the ridge dimensions were established and the study of the spatial variation of the consolidated layer showed that ridges grew evenly in width
• Studying the consolidation and the transition from 1st year to 2nd year ridges in the Fram Strait

Lucie Strub-Klein
Born in Schiltigheim (Strasbourg), France in 1984. Studied civil engineering in The National Institute for Applied Science (INSA) in Strasbourg with specialization in construction, steel and concrete design, bridge design, material properties. Master in sea ice rheology in cooperation with UNIS. Started PhD at UNIS/NTNU on 27th August 2007.

MSc Kjell Karlsrud har til forsvar for graden dr.philos. ved Norges teknisk-naturvitenskapelige universitet innlevert avhandling med tittel:

"Prediction of Load-Displacement Behaviour and Capacity of Axially Loaded Piles in Clay Based on Analyses and Interpretation of Pile Load Test Results"

Til å bedømme avhandlingen er oppnevnt:
- Professor Harry Poulos, University of Sydney, Australia (1. opponent).
- Dr.ing. Arne Åsmund Skotheim, Norconsult AS, Norge (2. opponent).
- Professor Steinar Nordal, Institutt for bygg, anlegg og transport, NTNU.

Professor Steinar Nordal er oppnevnt som administrator for bedømmelseskomiteen.

Prøveforelesningen over selvvalgt emne vil bli holdt i Totalrommet, Hovedbygningen, Gløshaugen onsdag 18.04.12 kl. 13:15 over emne:

"Design and Performance of Deep Excavations in Soft Clay"

Prøveforelesningen over oppgitt emne vil bli holdt i Rådssalen, Hovedbygningen, Gløshaugen torsdag 19.04.12 kl. 10:15 over emne:

"Geotechnical Challenges Arising From a Possible Global Sea Level Rise"

Disputasen avholdes i Rådssalen, Hovedbygningen, Gløshaugen torsdag 19.04.12 kl. 13:15

M.Sc. Tanu Priya Uteng har til forsvar for graden philosophiae doctor (ph.d.) ved Norges teknisk-naturvitenskapelige universitet innlevert avhandling med tittel: 

"Transport-related Social Exclusion: Incorporating Imperatives of Gender and Age in the Transport Planning Processes"

Til å bedømme avhandlingen er oppnevnt:
- Senior Research Fellow Karen Lucas, University of Oxford, UK (1. opponent)
- Professor Petter Næss, Aalborg Universitet, Danmark   (2. opponent)
- Førsteamanuensis Eirin Olaussen Ryeng, NTNU

Førsteamanuensis Eirin Olaussen Ryeng er oppnevnt som administrator for bedømmelseskomiteen.

Hovedveileder for doktorgradsarbeidet har vært professor Tore Øivin Sager.

Prøveforelesningen vil bli holdt i Totalrommet, Hovedbygningen, Gløshaugen tirsdag 17.04.12 kl. 10.15 over emne:

  "Methodological Challenges in Cross-National Comparative Mobility Studies"

 Disputasen avholdes samme sted

The thesis deals with three main topics:

1. Rubble accumulation in front of an ice barrier: A thorough qualitative description of the ice failure mode during interaction is done and a quantitative analysis from image analysis gave values for breaking length and block size of the rubble accumulation.
2. Rubble accumulation in the form of model ridges: A review on the state of the art in the topic is presented along with a study in two "cold" and two "warm" model ice ridges and its thermo-mechanical properties.
3. Freeze-bonds: The most extensive part of the thesis deals with freeze-bonds. The thesis presents how the freeze-bond shear strength varies with key parameters, such as initial ice temperature, normal confinement and contact time. Their study allows presenting a 1D mechanical model for the freeze-bond deformation and failure description. The last part of the thesis presents 2D rubble and freeze-bond experiments linking rubble failure and freeze-bond failure.