Stability controls in subsurface interfaces subjected to thermal and mechanical actions
- Reference no.
- Closing date
Dr Melis Sutman, Heriot Watt University
Dr. Sadegh Nadimi, Newcastle University
Dr. Elli-Maria Charalampidou, Heriot Watt University
Dr. Ali Ghanbarzadeh
University of Leeds
Understanding the response of geo-materials and civil infrastructure to thermo-mechanical actions is crucial for the shallow geothermal energy exploitation. Energy geostructures enable the use of renewable energy sources for efficient heating and cooling of buildings, by combining their conventional structural support role with the contemporary one of heat exchange . Therefore, any structure (energy piles, walls, tunnels) in contact with geo-materials can be equipped with geothermal loops, connected to a ground source heat pump, allowing heat exchange with the ground (Fig. 1). Energy geostructures research has so far focused on in-situ tests , laboratory-scale tests  and numerical tools , aiming to understand cyclic temperature change effects (triggered by geothermal operations) on the behaviour of geomaterials, infrastructures and their interfaces. Yet, emphasis was on soils and soil-concrete interfaces, overlooking the impact of shallow rock formations. The latter has recently attracted concerns following an in-situ test on energy piles whose bottom portions were socketed in sandstone . Results showed that the pile portion within the sandstone experienced tensile stresses during heat injection into the ground; the inverse of what would be expected had the pile been embedded entirely in soils. Although this observation was attributed to larger thermal expansion of sandstone (vs that of soil or concrete), a thorough understanding of this phenomenon has never been investigated to date.
The thermo-mechanical response of soil-rock interfaces can also be linked to the global temperature increase (up to 10ËšC in cities by 2080), which will affect soils, rocks and their interface particularly in shallow depths. Finally, undisturbed ground temperature is highly affected by human activities, such as the operation of underground systems, which increases the ground temperature in urban environments (5-14ËšC temperature increase around London Underground). Considering infrastructure in mixed-face ground, the soil-rock interaction will become increasingly crucial due to temperature variations.
Extensive research was performed on mechanical behaviour of soil-structure interfaces , limited efforts were also devoted to temperature effects on soil-concrete interfaces . According to these studies, depending on the concrete surface roughness and soils’ mean grain size, three failure mechanisms can occur: shear failure within the soil for rough surface, sliding at the interface for smooth surface, simultaneous shear and sliding at roughness close to the critical one. Limited research on thermal effects showed that sand-concrete interface has fairly thermo-elastic behaviour whereas clay-concrete interface shows decrease in interface friction angle and increase in adhesion with temperature rise. Yet, how the aforementioned knowledge can be applied to soil-rock interfaces is still obscure due to several differences concrete and rock interfaces possess: (i) soils around concrete structures are usually disturbed due to construction efforts, the ones around rock formations are naturally deposited over long geological periods; (ii) concrete structures usually have uniform roughness, rock surfaces might have irregularities; (iii) concrete structures are usually accepted as isotropic, rock formations can exhibit highly anisotropic behaviour. Regarding these disparities, an extensive experimental investigation of soil-rock interfaces considering confining pressure, surface impurities and rock anisotropy is essential, the outcomes of which will benefit geoenergy, climate change and urban heat island fields.
Further project details are available on the IAPETUS2 website.
All applicants need to meet NERC’s eligibility criteria to be considered for an IAPETUS studentship and these are detailed in the current UKRI studentship terms and conditions.
IAPETUS2 is only able to consider applications from Home/European Union candidates. International candidates are not eligible to be considered and where an candidate from another EU country has not been resident in the UK for 3 years or more prior to the commencement of their studies with IAPETUS2, they will only be eligible for a fees-only studentship.
IAPETUS2 is looking for candidates with the following qualities and backgrounds:
A first or 2:1 undergraduate degree, or have relevant comparable experience – we welcome applications from those with non-traditional routes to PhD study;
In addition, candidates may also hold or be completing a Masters degree in their area of proposed study or a related discipline; &
An outstanding academic pedigree and research potential, such as evidenced through the publication of articles, participation in academic conferences and other similar activities.
IAPETUS2’s postgraduate studentships are tenable for up to 3.5 years, depending on the doctoral research project the student is studying and provides the following package of financial support:
A tax-free maintenance grant set at the UK Research Council’s national rate, which in 2019/20 is £15,009.
Full payment of their tuition fees at the Home/EU rate;
Access to extensive research support funding; &
Support for an external placement of up to six months.
Part-time award-holders are funded for seven years and receive a maintenance grant at 50% of the full-time rate.
How to apply
Prospective applicants must apply to both Heriot Watt and to IAPETUS directly by 5pm on Friday 10th Januiary 2020.
Please complete our online application form.
Please select PhD programme in Civil Engineering and include the reference IAPETUS2-19 on your application. You will also need to provide a CV, supporting statement (this should be uploaded to the project proposal field on the application form), a copy of your degree certificate and relevant transcripts, and one academic reference. You must also provide proof of your ability in the English language (if English is not your mother tongue or if you have not already studied for a degree that was taught in English). We require an IELTS certificate showing an overall score of at least 6.5 with no component scoring less than 6.0.
For informal enquiries, contact:
Dr. Melis Sutman
January 10, 2020 5:00pm
Deadline for prospective students to apply for a studentship
January 15, 2020 5:00pm
Deadline for students who have applied to more than one project to decide which project to proceed with
February 11, 2020 5:00pm
Shortlisted candidates will be contacted with an invitation to interview.