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Geophysical assessment and grout injection of estuary and reservoir embankments subject to badgers burrows erosion

ABG-87399 Thesis topic
2019-09-12 > €25,000 and < €35,000 annual gross
University of Strathclyde (CEE Dpt) - Paul Sabatier University/INSA Toulouse (LMDC)
Glasgow - United Kingdom
Geophysical assessment and grout injection of estuary and reservoir embankments subject to badgers burrows erosion
  • Materials science
  • Civil engineering, construction and public works
  • Engineering sciences

Topic description

Background.

Stability of rivers and reservoirs embankment slopes covers a wide range of problems, from seepage to catastrophic collapse triggered by flooding. The recent events in 2013 in UK have highlighted the need for reliable distributed monitoring techniques to assess the integrity of reservoirs and river embankments and also slopes in general for landslide and slip surfaces. Flooding is a direct threat to inhabitants safety and the economy when roads or rail tracks are cut. The failure modes of earth flood defences can be the consequence of cracking and erosion due to desiccation or to the presence of animal burrows. Very little information is known in a detailed and distributed manner about the mapping of the fissuring and burrows network and also about the level of saturation of the slopes. Common Geotechnical sensors like Tensiometers for soil suction, Theta probes for moisture measurements are not distributed and give local point measurements. Hot spots and preferential water seepage pathways can be missed. Trenching is a work intensive. It is a time consuming process and destructive to the embankment structure, there is also a high risk that the trench does not reveal the full extent of the damage.

According to studies, 46 % of dams and embankments failures are due to severe internal erosion. Animal burrowing can lead to a preferential path for the water flow and seepage through the flood embankments that could lead to a partial or total collapse of the structure. A few tragedies occurred worldwide in the past decades due to flooding and animal burrowing, causing considerable damages (Trackle canal in Nevada 2008, Mallard Lake TN 1996 or the prospect reservoir Dam in 2002). Badger's tunnelling is usually shallow from 0 to 2 m, and in a deep slope allowing a better runoff for a better stability of soil. Previous Geophysical studies were undertaken in order to detect the extent of the setts in the Humber Estuary by the Environment Agency. Geophysical survey can provide additional information about water seepage pathway that could inform Geotechnical analysis on the failure mechanisms of embankments and the influence of animal burrows in the process.

Methodology:

Detection.

It is proposed to use the classic terrestrial electromagnetic survey measuring soil conductivity (ie saturation) using a CMD2 (Depth coverage 1.5m to 3m) used by the team at Strathclyde coupled with latest CMD mini explorer (GF instruments) that can scan a depth of soil from ground level to 1.5m depth,  screening 0.5m thick layers of soil simultaneously and capable to invert the results and compare directly with Electrical Resistivity Tomography technique (ERT). The CMD mini-explorer is using its own inversion algorithm to extrapolate conductivity results to resistivity. Hence it allows to invert the results without the need to install the whole ERT system with electrodes and cables on the slope where access is awkward. An airborne electromagnetic survey will also be carried out by the Academic project partner (French University EOST from Strasbourg France). Their team has developed an electromagnetic drone that will be tested on the slope. Both terrestrial and airborne conductivity surveys will be compared in order to establish the final map of the burrows. Additional ERT and Ground Penetrating Radar measurements will be carried out to establish and map the complete burrows network.

Repairs.

Grouts will be made to fill in the burrows and voids and geophysics will be used again to assess the completion and effectiveness of the repairing process. LHOIST Belgium, industrial partner of the project, and LMDC, academic partner, will formulate grouts from numerical simulations and rheological tests and will welcome the PhD student to access their laboratory testing facilities in Belgium, UK and France, respectively.  Field testing will be facilitated by the Environment Agency on practical case studies near the Humber Estuary. Both LHOIST and the Environment Agency will offer time in kind. LHOIST will offset the University cost for the student stipend (£3K / year) on top of the use of their facilities in UK and Belgium for the grout formulation and Geotechnical analysis.

General Aims:

To inform the risk of badgers burrows network based on Geophysical conductivity/saturation mapping of river, estuary and reservoir embankment slopes.

To assess the efficiency and completion of repair grouts injections inside the badgers setts.

Specific Objectives:

•             To establish a map of the burrows network inside embankments slopes at different depths (0.5m increments) covering the common thickness of transitional landslides and embankments slope slip surface and landward face failure after overtopping or seepage.

 

•             To provide a risk evaluation map based on Geophysical sensors data and slope stability software (Electrical Resistivity Tomography, Ground Penetrating Radar and Geoslope)

 

•             To identify numerically optimized rheological parameters of grouts (injection factors, i.e. time, flow rate/pressure, temperature, etc.)

 

•             To design grouts from mixture experiments strategy

 

•             For the methodology to be adopted in the future by companies like Atkins and Mott Mac Donald and by the Environment Agency for reservoir safety and river embankments integrity long term monitoring.

Starting date

2019-11-01

Funding category

Public/private mixed funding

Funding further details

Scholarship (University of Strathclyde -UOS) £16 000/year - the University cost for the student stipend (£3K / year) is offset by LHOIST group

Presentation of host institution and host laboratory

University of Strathclyde (CEE Dpt) - Paul Sabatier University/INSA Toulouse (LMDC)

The research is strongly aligned to Strathclyde University’s vision of a leading international technological university. The fast scan Geophysical techniques (electromagnetic) to be deployed have the potential to be implemented not only for river and embankment slopes but also for the remote monitoring of slope and landslides that are causing serious disruption for roads in Scotland. This research will allow Strathclyde to lead pioneering innovative remote scanning technology. In addition, this project aligns with Strathclyde’s ambition to challenge traditional academic boundaries to solve climate change engineering problems. It is a cross-disciplinary research in Geophysics (Dr Sentenac, Strathclyde University), in Geotechnics (Dr Gontran Herrier, LHOIST Belgium) and in material engineering (Dr Mouret, Dr Papon, LMDC, UPS/INSA) for the development of repair grouts to fill in burrows and fissures in the laboratory and on the field. 

PhD title

PhD - Civil and Environmental Engineering

Country where you obtained your PhD

United Kingdom

Institution awarding doctoral degree

University of Strathclyde

Graduate school

Candidate's profile

You must have, or expect to achieve, at least a 2:1 honours degree or international equivalent, in Civil Engineering or a relevant subject. Experience conducting both numerical and experimental/field test research would be an advantage, but is not essential. The candidate will be expected to conduct work with international academic partners and should have good interpersonal skills.

An overall score of IELTS 6.5 or equivalent is required, with individual scores of 6.0 in each of the four sub-skills: writing, reading, speaking and listening.

Important points:

Research Council (RC) fees and stipend can only be awarded to UK and EU students and not to EEA or International students.

EU students are only eligible for RC stipend if they have been resident in the UK for 3 years, including for study purposes, immediately prior to starting their PhD.

If an EU student cannot fulfil this condition then they are eligible for a fees only studentship.

International students cannot be funded from RC funds unless they are ‘settled’ in the UK. ‘Settled’ means being ordinarily resident in the UK without any immigration restrictions on the length of stay in the UK. To be ‘settled’ a student must either have the Right to Abode or Indefinite leave to remain in the UK or have the right of permanent residence in the UK under EC law. If the student’s passport describes them as a British citizen they have the Right of Abode.

Students with full Refugee status are eligible for fees and stipend.

Application deadline

2019-10-14
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