ESR-9-01

Micro-mechanics of failure planes

Ricarda Gatter | Marum

Research

Almost 20 years ago, in July 1998, a tsunami struck Papua New Guinea and devastated three villages, causing the death of over 2200 people. In 1996, a landslide initiated offshore Finneidfjord, Norway, and removed a 250 m long section of the main north-south highway, due to the slide’s retrogressive behaviour. Although these events highlighted the importance of submarine landslide research, the potential hazard related to submarine landslides was already recognised in 1929. A large slide and the flow of sediment it generated broke telecommunication cables off Grand Banks. However, to enable the assessment and effective mitigation of this hazard, one needs to understand the underlying mechanisms first. What causes submarine landslides? What are the pre-conditioning factors and triggering mechanisms? How do submarine landslides behave during runout?

I focus on the factors that pre-condition slope failure. Many stud­ies have shown that basal fail­ure planes of sub­mar­ine land­slides co­in­cide with mech­an­ic­ally weaker lay­ers em­bed­ded within the slope strati­graphy. Pore pres­sure fluc­tu­ations along po­ten­tial weak lay­ers, e.g. em­bed­ded vol­canic ashes or fos­silifer­ous soils whose particles can break down un­der load­ing, can de­crease the shear strength of the sed­i­ments and hence, un­der­mine slope sta­bil­ity. Al­though many stud­ies have assessed the influence of sed­i­ment com­pos­i­tion on the phys­ical prop­er­ties and shear strength of sediments, the processes oc­cur­ring prior and dur­ing the ini­tial fail­ure are still poorly un­der­stood, as these can­not be dir­ectly ob­served or mon­itored. In this project, I will conduct a number of 3D numerical shear experiments, utilising granular simulation techniques (e.g., PFC3D), to investigate the failure processes at the initial stages of submarine landslides.

Methods

In a first step, I will compile a comprehensive dataset of µ-CT (micro- Computed Tomography) measurements of a wide range of sediment cores from different submarine landslides. These include cores from the Finneidfjord Slide (Norway), the AFEN Slide (UK), the Twin Slides (Italy), the Cap Blanc Slide (NW Africa), and the Tuaheni Slide (New Zealand). From this dataset, I will gather compositional and textural information of the material near the basal failure planes of the slides. The resulting information will directly act as input data for the numerical models.

By means of the 3D numerical simulations, which mimic geotechnical shear tests on a micro-(grain)-scaled level, I will investigate the fabric evolution of different materials under shearing with time. Of particular interest will be (A) a simplified ash and (B) a diatom sediment, and the changes in their shearing behaviour due to variations in the ash and diatom contents. The grain-scaled level is necessary in order to discern the spatial and temporal evolution of shear zones. Where does strain accumulate and where do basal failure planes form (above, inside, or below the weak layer)? This information is necessary to gain a deeper understanding of the failure mechanism and hence, the slide evolution itself.

Hosting institute
 
 
Working Group
  • Modelling of Sedimentation Processes
Supervisor
PDP Committee members:

TEAM

Ricarda Gatter
PhD student – ESR 9
rgatter@marum.de
Katrin Huhn-Frehers
Principal Investigator – ESR 9, 11
khuhn@marum.de

NEWS

2020 | 2019 | 2018 |

2020

18/05/20
The EGU GA 2020 – a little different
@ Sharing Geoscience Online (4-8 May)
ESR 10, ESR 2, ESR 4, ESR 5, ESR 6, ESR 9, News
 

The biggest geoscience conference in Europe went online this year – but did it work? Read what our ESRs thought about this year’s EGU General Assembly, as conveners, authors/presenters and visitors.

18/02/20
Recap of 2019
ESR 9, General, Miscellaneous, News, Secondments
 

A year full of setbacks and progress, re-adjustments and developments, learning and new discoveries, but most importantly exciting science: Ricarda recalls her experiences of 2019.

2019

30/10/19
Bologna Workshop – A discovery of turbidites or maybe more?
@ CNR-ISMAR Bologna, Italy (15 – 21 September 2019)
ESR 13, ESR 9, General, News
 

What are turbidites? What do they look like? And why should we care? Find out what our ESRs discovered during their third annual SLATE meeting and what else happened during the week in Bologna.
23/07/19
Impressions from the EGU 2019
@ Vienna, Austria (07 – 12 April 2019)
Conferences, ESR 1, ESR 12, ESR 13, ESR 14, ESR 15, ESR 2, ESR 3, ESR 4, ESR 5, ESR 6, ESR 7, ESR 8, ESR 9, News
 

ESRs share their experience at the EGU General Assembly 2019 hosted in Vienna, Austria. Posters, oral presentations, PICOs and much more.

24/01/19
ESRs’ experiences of the BSRG2018
@ Edinburgh, Scotland (18-19 Dec 2018)
Conferences, ESR 10, ESR 5, ESR 9, News
 

Kate (ESR5), Ricarda (ESR9) and Maarten (ESR10) participated at the British Sedimentological Research Group Annual Group Meeting (BSRG AGM 2018), which was held the 19th and 20th of December 2018 in Edinburgh, United Kingdom. Read about their experiences of this conference here!

2018

04/12/18
GLOMAR – the Bremen International Graduate School of Marine Sciences
Courses, ESR 11, ESR 7, ESR 9, News
 

Graduate schools can provide PhD students valuable support in a variety of ways. In this blog, Ting-Wei (ESR 7), Ricarda (ESR 9) and Monika (ESR 11) introduce GLOMAR, the international graduate school for marine sciences in Bremen. Read more about networking opportunities, seminars and offered courses!
19/06/18
Ricarda’s report on her 2nd secondment
@ NOCS / University of Southampton
ESR 9, News, Secondments
 

After a first, shorter secondment at NOCS and the University of Southampton in February, Ricarda returned to Southampton in May to continue her work on µCT (micro-Computed Tomography) data, focussing in particular on data from the AFEN Slide (UK) and the FInneidfjord Slide (Norway).
18/06/18
Review of ECORD Training Course 2018
@ MARUM, Bremen, Germany
ESR 11, ESR 2, ESR 3, ESR 4, ESR 6, ESR 7, ESR 9, News
 

From 23rd to 27th April, a group of seven SLATE ESRs participated in the ECORD Training Course 2018, which took place at MARUM – Center for Marine Environmental Sciences, Bremen. This one-week course provided a “Virtual Ship Experience” and prepared the young researchers for sailing in an offshore drillship expedition.
24/05/18
Ricarda’s report on her 1st secondment
@ NOCS / University of Southampton
ESR 9, News, Secondments
 

In my PhD project, I investigate factors that pre-condition submarine slopes to fail. I focus on the characterisation of the material near the basal failure planes of different slides and the material’s behaviour prior and during the initial stages of slope failure. The processes occurring prior and during failure are still poorly understood, as they cannot be directly observed or monitored, at least not on a grain-scaled level.