Temaer for prosjekt- og masteroppgaver

Basert på vår erfaring med veiledning og oppgaver viser vi nedenfor eksempler på forslag til prosjekt- og masteroppgaver med veiledning fra NGI. Selve innholdet vil utarbeides i samarbeid med student, veileder ved universitetet og NGIs veileder. En sommerjobb på NGI kan ofte være inngangen til kontakt med fagekspert på NGI for valg av prosjekt- eller masteroppgave. Her er en liste over titler/temaer for slike oppgaver. Nedenfor er det en kort beskrivelse av disse.

  1. Effekt av temperatur på målte lab-data
  2. Jordskjelvlaster på kjellervegger og tuneller
  3. Numerical (and experimental) modelling of a new laboratory testing device for establishing monotonic and cyclic p-y curves for piles
  4. Analyse av temperatur og strekkbelastning på brustruktur
  5. Etterregning og modellering av korte stålkjernepeler utstøpt med bentonittsement
  6. Egenskaper av kalksementstabilisert leire
  7. Influence of organic matter on the geotechnical properties of silts
  8. Spudcan punch-through risk in sand over clay soils
  9. Spudcan combined bearing capacity in sand over clay soils
  10. Model to predict equivalent number of cycles from earthquake shaking
  11. From Rho to Q – correlation of geophysical parameters to the Q-value
  12. SlopEM - Geophysical mapping of bedrock in steep terrain
  13. Pile group response, improved procedures based on calibration with FEA
  14. Lateral response of piles in sand
  15. Set-up and ageing of axial pile capacity
  16. Back-analysis of pile installation data
  17. Submarine slope stability under earthquake loading
  18. Material strength anisotropy under different stress conditions and different stress histories (Laboratory testing)
  19. Database of cyclic soil properties
  20. Effective stress based versus total stress based foundation design in sand
  21. Effect of trenching on bearing capacity of suction caisson in clay
  22. Probability based design of suction caisson bearing capacity
  23. Cyclic axial walking of pipelines in clay

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1. Effekt av temperatur på målte lab-data

NGI har et pågående forskningsprosjekt i samarbeid med industrien for å se på effekten av temperatur på de parameterne man måler i standardiserte laboratorieforsøk, som triaks- og ødometerforsøk. I denne oppgaven skal det undersøkes temperatureffekt på kvikk leire fra NGTS - Norwegian Geo-Test Sites testområde som er under etablering i Trondheim. Forsøkene vil inngå i en større registrering av jordparametere for senere bruk i forskning.

Prosjektoppgave: Gjennomgå problemstillingen og tilgjengelige data.

Hovedoppgave: Bruke NGIs og/eller NTNUs klimarom. Kjøre parallelle forsøk ved forskjellige temperaturer, for eksempel på materialer som er dokumentert på tidligere.

Kontaktpersoner:

NTNU:

  • arnfinn.emdal@ntnu.no 9754 7729

NGI:

  • Tom Lunne, tlu@ngi.no, T: 22 02 30 54, M: 900 29 267
  • Morten Sjursen, mas@ngi.no, T: 22 02 3066, M: 476 00 553

2. Jordskjelvlaster på kjellervegger og tuneller 

Jordskjelvlaster på støttekonstruksjoner er ofte beregnet ved hjelp av en metode som er utviklet av Mononobe-Okabe. Denne metoden har blitt basis for formelverket i de fleste standarder slik som for eksempel Eurocode 8. En variant av denne metoden brukt for laster på kjellervegger er delvis basert på resultater av teoretiske analyser av bølgeforplantning i jord bak fast-innspente vegger. I realiteten beveger en kjeller seg i forhold til jordskjelvbølger, og avhengig av konstruksjonens dynamiske egenskaper kan lasten på kjellerveggen være større eller mindre enn det som er gitt i standarder. I tuneller går forholdene mer i retning av at laster blir mindre.

Formålet med oppgaven er å utføre et litteraturstudie over teoretiske og numeriske løsninger og for å identifisere modellforsøk som kan brukes til verifisering av nye modeller. Det er ideelt med noen innledende PLAXIS analyser for å bli kjent med mekanismene og bruk av PLAXIS i jordskjelvanalyser. Oppgaven kan danne grunnlag for en masteroppgave på samme tema med detaljerte analyser og vurderinger.

Kontaktpersoner:

 

3. Numerical (and experimental) modelling of a new laboratory testing device for establishing monotonic and cyclic p-y curves for piles

NGI has developed a new laboratory testing device which can be used to establish monotonic and cyclic p-y curves for offshore piles and conductors. Main focus was to establish soil-foundation response due to small strain cyclic loading.  Comparisons with field tests and centrifuge tests revealed the suitability of the device to establish reasonably accurate curves for this purpose. However, many other aspects, which were not considered during the development, remain unclear and the actual capabilities and limitations of the device are still unidentified.

NGI

 New laboratory testing Device (left) and results from numerical analysis of lateral loading of a pile

The objective of this work is to identify the capabilities and limitations of the device. This should be achieved primarily by means of numerical analyses. A parametric study using 2d and/or 3d FEM model(s) should be performed by varying soil properties, soil state, and loading conditions. Based on a critical review of the numerical analyses, the capabilities and limitations of the device can be identified and a numerical database can be established. If time allows, the student has the possibility to get familiar with the device and to verify his numerical model by performing own tests in the device.

The project assignment should start with a comprehensive literature review on p-y curves and relevant models tests. In addition some few laboratory tests can be performed in order to understand the device and to identify open questions, which allows to narrow the literature survey. The master thesis should comprise of the numerical analyses including evaluation and review of the numerical results. The results of the literature review should help to critically review the own numerical analyses.

Kontaktpersoner:

 

4. Analyse av temperatur og strekkbelastning på brustruktur

NGI installerte i 2008 et omfattende fiberoptisk målesystem på Gøtaelv bru i Gøteborg. Siden installasjonen har det hver fjerde time blitt logget temperatur og strekkbelastning i flere tusen punkter på brua, akkumulert er dette et stort datasett.

Prosjektoppgave: Analysere kort- og langtidsdrift i måledata og relatere dette til temperatursvingninger.

Masteroppgave: Analysere kort- og langtidsdrift i måledata og relatere dette til temperatursvingninger. Beregne temperaturkompenserte strekkmålinger. Foreslå strategi for temperaturkalibrering av fiberoptiske strekkmålinger.

Kontaktpersoner NGI:

 

5. Etterregning og modellering av korte stålkjernepeler utstøpt med bentonittsement

Problembeskrivelse Når det skal benyttes stålkjernepeler under stive konstruksjoner og dybden til berg er relativt liten, får stålkjernene en store tvangskrefter over kort lengde. Stålkjernepeler settes som stålsylindere i en capping av mørtel inne i et foringsrør, og alle de tre elementene får deformasjoner på grunn av kreftene. Mørtelen er i utgangspunktet kun en korrosjonsbeskyttelse for stålkjernen, men påvirker den ferdige pelens stivhet og må tas med i beregningene. Det samme gjelder foringsrøret.

Ved Nytt Nasjonalmuseum er det etablert stålkjernepeler hvor mørtel-cappingen er erstattet med en sement tilsatt bentonitt, for å oppnå et mindre stivt konstruksjonselement. Vi ser for oss at metoden kan utvides og brukes på generelt grunnlag, dersom det kan utarbeides en modell som gjelder flere innspenningstilfeller, lastsituasjoner og mørtelfasthet.

Leveranse Prosjektoppgaven foreslås innledet med en beregningsmessig dokumentasjon av stålkjernepeler utført på tradisjonelt vis med fokus på deformasjon ved ulike innspenningsforhold i topp (ev. også i bunn). Flere standard-dimensjoner kan kartlegges, da mørteltykkelse og foringsrørets tykkelse også varierer for de ulike peledimensjonene som er i handelen.

Videre kan det sees på en utvalgt peledimensjon for å belyse effekter av en mykere mørtel og over hvilken lengde den skal støpes ut. Det er et stort spillerom for variasjoner her. Modellering og beregninger kan utføres i Plaxis og suppleres med GeoSuite for å se hvordan modellen kan integreres her.

Forventet tid 2 semestre, men oppgaven kan tilpasses å være kun prosjekt- eller kun master-oppgave.

Datagrunnlag Data fra blant annet Nasjonalmuseet og andre prosjekter NGI er involvert i.

Studentens bakgrunn Mastergradstudier i tekniske geofag og/eller konstruksjonsfag. Oppgaven kan også løses av to studenter, en med fokus på materialer og en med fokus på statikk.

NGI-veiledere: 

 

6. Egenskaper av kalksementstabilisert leire

Problembeskrivelse Ved installasjon av kalksementpeler i felt er det oppnådd høyere skjærfasthet i det stabiliserte materialet enn hva som oppnås når en blander inn kalksement i en kjøkkenmaskin på laboratoriet. I enkelte tilfeller, særlig fra innblanding i kvikk og siltig leire i Trøndelag er det observert svært høy fasthet av det stabiliserte materialet.

I denne sammenheng har NGI derfor begynt å etablere en kalksementdatabase hvor det forsøkes å samle inn erfaringer med stabilisert leire.

I forbindelse med byggingen av E6 Jaktøyen-Storler utenfor Trondheim vil det installeres ca. 45 000 kalksementpeler i løpet av den nærmeste perioden og det vil utføres en stor mengde felt- og laboratorieundersøkelser på materialet for å undersøke styrke- og deformasjonsegenskaper av det stabiliserte materialet.

Leveranse Prosjektoppgaven foreslås innledet med litteraturstudie knyttet til egenskaper av kalksementstabilisert leire. I studiet inngår også bruk av NGIs database for å se på mulige korrelasjoner.

Masteroppgaven viderefører arbeidet som er utført i prosjektoppgaven hvor flere ulike problemstillinger kan være relevant. Både behandling av databasen, felt- og/eller laboratorieforsøk på materiale fra E6 kan være aktuelt, avhengig av framdriften til anleggsarbeidene og studentens egne ønsker.

Oppgavebesvarelsen skal inneholde beskrivelse av de gjennomførte analysene, hovedresultater og relevante vurderinger.

Forventet tid 1-2 semestre

Datagrunnlag Data fra en rekke prosjekter NGI har vært involvert i.

Studentens bakgrunn Mastergradstudier i Bygg- og miljøteknikk.

NGI-veileder

  

7. Influence of organic matter on the geotechnical properties of silts

Problem description Intermediate silty soils are challenging materials in geotechnical engineering, and limited information on their engineering properties and how these relate to the geological background is available. This is primarily due to uncertainty in material behaviour, difficulties associated with sampling undisturbed material and the interpretation of in situ and laboratory test data. There is a need to provide guidance to practicing geotechnical engineers regarding characterization of silty material.

The Halden research site is being develop has a reference site for geotechnical characterization of intermediate soil within the SP8-GEODIP and National Geo-Test Site projects. Here, results from in situ investigation and soil testing show that patterns of water content, unit weight, magnetic susceptibility, engineering parameters and cone penetration resistance are affected by subtle changes in organic content. Reasons for these gradual change are not fully understood and further studies are necessary.

Student task The project assignment should start with a broad literature study looking at the influence of organic matter on the behavior of geomaterials such as clay, silt and sand.

Later in the MSc. work, the student should perform laboratory investigations to further test the influence of organic matter on the geotechnical behavior of silt. The laboratory investigation should include, for example, triaxial and oedometer tests, and microscopy analyses. Data from the Halden research site will be available. The data set will be completed with a large database of in situ test results available at the research site (e.g. CPTU data, dissipation test results, etc).

Estimated time 2 semester (prosjektoppgave + master oppgave)

Source of data Data from the Halden Research site and access to NGIs database.

NGI supervisor(s): 

  

8. Spudcan punch-through risk in sand over clay soils

Problembeskrivelse Self-elevating jack-up rigs are widely used for offshore drilling activities. The rigs are typically equipped with circular foundations called "spudcan". During installation, the spudcan foundations are penetrated into the seabed under a predetermined "preload" by water ballast.

One of the common challenges during the installation phase is the punch-through risk where the spudcan penetrates rapidly in an uncontrolled manner. This typically occurs when the spudcan penetrates through a strong layer underlain by a weak layer. In many cases with a sand over clay soil profile, punch-through risk is suggested using standard methods recommended in industry guidelines.

Whereas a detailed analysis, for example, by means of running a large deformation finite element analysis, reveals little risk as the load-penetration curve increases monotonically with depth. It is therefore useful to find out what combinations of parameters (spudcan diameter, sand layer thickness, clay strength and etc.) lead to punch-through risk and what combinations rule out the risk.

Leveranse Extensive numerical/experimental studies have been performed in the last decade in related to jack-up punch-through risk in sand over clay soils. This project aims for complementing existing understanding by investigating parameter ranges that have not been studied previously, but are still relevant for practical engineering. The ultimate goal of the project is to come up a simple model that predicts when punch-through risk can be ruled out in a sand over clay soil profile.

The study will involve: 1) a comprehensive literature study, 2) getting familiar with FEM tool, Abaqus CEL, which is suited for modelling the large deformation process during spudcan penetration; 3) developing and benchmarking numerical models; 4) identifying dimensionless parameter groups that control the response and performing parametric analyses; 5) formulating predictive models/recommendations; 6) writing-up thesis/report.

Forventet tid 2 semesters

Datagrunnlag None

Studentens bakgrunn Master student in geotechnical engineering

NGI veiledere:

 

9. Spudcan combined bearing capacity in sand over clay soils

Problembeskrivelse Self-elevating jack-up rigs are widely used for offshore drilling activities. The rigs are typically equipped with circular foundations called "spudcan". During installation, the spudcan foundations are penetrated into the seabed under a predetermined "preload" by water ballast. In a jack-up site specific assessment which evaluates the suitability of a rig to a certain location, the spudcan in-place stability under storm loading must be assessed. This requires knowledge of the bearing capacity of the spudcan under combined vertical (V), horizontal (H) and moment (M) loading, which is typically expressed in VHM interaction envelopes.

Current industry guidelines provide mathematical formulas for the spudcan capacity envelopes in either pure sand or pure clay soils. For a spudcan embedded on a sand over clay profile, question arises on what bearing capacity envelope should be used? Could preferential failure mechanism develop in the underlying clay layer?

Leveranse The project aims for providing practical recommendation of capacity envelopes for a spudcan embedded on sand underlain by clay.

The study will involve: 

  1. a comprehensive literature study
  2. getting familiar with FEM tool, Abaqus Standard/Plaxis 3D
  3. developing and benchmarking numerical models
  4. identifying dimensionless parameter groups that control the response and performing parametric analyses
  5. formulating predictive models/recommendations
  6. writing-up thesis/report.

Forventet tid 2 semesters

Datagrunnlag None

Studentens bakgrunn Master student in geotechnical engineering

NGI veiledere:

 

10. Model to predict equivalent number of cycles from earthquake shaking

Problembeskrivelse The number of shear strain cycles strongly influences the build-up of pore water pressures during earthquake shaking, which can lead to soil degradation, liquefaction and landslides. There are a wide number of definitions of how to count cycles in a random signal, but relatively few prediction equations for earthquakes.

Leveranse The purpose of this research is to develop a predictive model to estimate the number of shear strain cycles from simple ground motion parameters such as magnitude and distance. The research will use the best available datasets, investigate several different counting methods, and use mixed effects regression to develop the best possible model. This research will provide much needed guidance that will help practicing engineers estimate seismically induced liquefaction and landslide hazards.

There is the possibility for collaboration with the Next Generation Liquefaction (NGL) project getting under way at the Pacific Earthquake Engineering Research Center (PEER) in Berkeley, California.

Forventet tid 2 semesters

Datagrunnlag Acceleration time series from the PEER NGA West 2 and NGA East ground motion databases, as well as from the KiK-NET database processed by Dawood et al (2016) and uploaded to the NEEShub. These are all freely available online.

Studentens bakgrunn Masters student in geotechnical engineering or engineering seismology.

NGI veileder:

11. From Rho to Q – correlation of geophysical parameters to the Q-value

The Q-system, which was developed at NGI, is widely used to classify rock masses in underground constructions as tunnels.

NGI has carried out several high resolution seismic and ERT (Electrical Resistivity Tomography) surveys in this decade for tunnel pre-investigations within large infrastructural projects Therefore core-drillings aligned to the geophysical lines were carried out and are available for further analysis. Based on the  geophysical results from projects we intend to correlate the obtained geophysical parameters to existing core-drillings and final correlation to the Q-value. The work will start with a literature study evaluating the existing relationships of the Q-system to electrical resistivities/seismic velocities and further investigate probabilistic relationships.

The work will be focusing on existing project-results and field-work is only optional. An interest in statistics is of advantage. Background in physical or engineering Sciences.

Kontakt:

12. SlopEM - Geophysical mapping of bedrock in steep terrain

The knowledge of the subsurface conditions is essential for all geotechnical projects and near surface geophysics are a well-established collection of methods to map and give a first insight into the ground. While standard methods as seismics and ERT (Electrical Resistivity Tomography) are widely used in many different settings the application of these methods becomes uneconomically and/or impossible in challenging topographical conditions. Conditions which are common due to Norway's geomorphology. We are therefore interested to evaluate different non-invasive electromagnetic methods in the frequency domain to map the bedrock surface in different geological conditions.

The project will start with a literature-study to investigate existing case studies, application of unconventional methods (e.g. VLF) and  an analysis of possibilities and limitations.

In a next step fieldwork will be carried out on different sites (tbd) and modelling of the acquired data. Due to the nature of the approach it might be necessary to adapt existing in-house  software solutions (background in Matlab and/or Python is an advantage) to implement a workflow.

Background in physical sciences (geoscience, physics, etc.).

Kontakt:

13. Pile group response, improved procedures based on calibration with FEA

Pile groups are widely used for supporting offshore structures, such as jacket platforms. Due to close proximity of the piles, the total capacity of a pile group might be less than the sum of the individual piles, resulting from the interaction between the piles within the group. In the design of the pile group foundations, the group effects are typically accounted for by applying reduction factors to the strength and stiffness of the pile group. As of today's practice, these factors are typically evaluated in a simplistic manner based on elasticity theory. Therefore, there is a need to perform research into this aspect in order to advance the current design practice.

This MSc program proposes to investigate this subject by means of advanced finite element analyses. The project will consist of 1) a comprehensive literature review of the past research in this subject area;  2) developing and benchmarking finite element analysis models; 3) Parametric finite element analyses, where a range of influencing parameters will be looked at, such as the geometric configuration of the pile group, the soil properties etc.; 4) recommendation of improved design method; 5) Evaluation of the impact of the new design method.

Contact person:

14. Lateral response of piles in sand

Steel pile piles are widely used as foundations or moorings for offshore structures, such as jacket oil platforms, floating production and storage facilities etc. In recent years, the development of offshore wind industry has also seen thousands of wind turbines founded on gigantic large diameter single pile foundations (commonly known as monopiles with diameter of 4-8 m and penetrated 20-40 m into the seabed). In design of offshore piles, in particular those for supporting offshore wind turbines, the lateral soil resistance and stiffness are essential design input.

In recent years, there has been a great deal of research on the lateral response of piles in sand by means of laboratory model testing, centrifuge model testing, field testing, and numerical simulations. Different researchers have proposed various models for calculating the lateral pile response. This MSc program proposes to carry out an assessment of the different models. The project consists of 1) a comprehensive literature survey and identify relevant models for assessment; 2) model evaluation by means of finite element simulations using advanced soil constitutive models and/or back -analyses of selected model/field pile tests; 3) Summary and recommendations.

Contact person:

15. Set-up and ageing of axial pile capacity

For piles driven in clays, several processes are considered to lead to a gradual increase in pile capacity with time: thixotropy (gain in soil shear strength without change in water contact); local redistribution of the excess pore pressures generated during driving, and; global dissipation of excess pore pressures. The combined effect of these three processes is commonly referred to as pile "set-up". Beyond set-up, there is also a long-term effect observed from pile testing, where the pile capacity increases with time. This is typically known as pile "aging".

This MSc project proposes to look at set-up effect for piles driven in clay. The key is to understand the time aspect, i.e. how much time the set-up process takes and the significance of the different set-up processes. This has an important practical significance since it governs the minimum waiting period before design loads can be applied to the pile foundations. The project will consist of 1) a literature review; 2) development and benchmarking of finite element models using existing field data; 3) parametric analyses; 4) summary and recommendations based on the numerical results.

Contact person:

16 Back-analysis of pile installation data

Prediction of pile installation resistance is an important design aspect for large pile foundations used offshore. This has great significance for choosing the appropriate hammer, management of the installation risks as well as fatigue design of the piles.

This MSc project proposes to perform an evaluation of different prediction methods for pile driving resistance against observed field installation records. Several technical questions will be investigated: 1) how well do the existing methods predict in comparison to field records; 2) do the existing methods work well for large diameter monopiles (with diameter 5-8 m) used for offshore wind turbines, noting that these methods were originally calibrated for smaller diameter piles (diameter 1.5-2.5m) used in the offshore oil and gas industry; 3) any adjustment or refinement of existing models for improved predictions?

The project consists of 1) collect and filter relevant pile installation records; 2) collect and evaluate design soil parameters for the installation records identified in 1); 3) back-analyses of installation records; 4) summary and recommendations.

Contact person:

17 Submarine slope stability under earthquake loading

Offshore landslides pose a major threat to subsea facilities, and one of the main triggering factors of offshore landslides is strong earthquakes. The state of the practice models offshore slope stability during strong shaking using one horizontal component of a selected representative ground motion. However, slopes and earthquakes are three-dimensional phenomena. Carlton and Kaynia (2016) performed 27 three-dimensional seismic slope stability analyses in PLAXIS to investigate the change in the predicted results when applying one, two, or three ground motion components. The results showed that applying two horizontal components instead of one may increase the predicted total displacements by 25% to 50%.

This study will build on the results of Carlton and Kaynia (2016) by performing a parametric analysis using a statistically significant dataset of ground motions, slope angles, and soil properties. The end result will be a simple model to estimate the permanent displacements from when 2 horizontal ground motion components are applied using the results of when only one component is applied.

This study will conduct the analyses using the program AMPLE2D, which was specifically developed to incorporate 2 ground motion components. AMPLE2D also uses the advanced constitutive model MSimpleDSS, which is an effective stress based model. The results will be compared with a smaller set of results using PLAXIS 3D.

Contact person:

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