Annual Report

such as elastic moduli, fracture toughness, and
mechanical heterogeneity, have on field-scale
hydraulic transmissivities
Experimental Investigation of the Thermo-
Hydro-Mechanical Behaviour of Soils
Researcher: Daniel Martinez Calonge
Supervisors: Dr Way Way Sim and Prof Lidija Zdravkovic
Sponsors: EPSRC and Geotechnical Consulting Group
In recent years, the study of the thermo-hydromechanical
(THM) behaviour of soils has been
a growing area of research within the geotechnical
community due to its importance in a wide
range of contemporary civil engineering applications
and activities, such as underground
nuclear waste storage, energy geostructures
or ground heat storage. The project firstly focuses
on the development of new experimental
capabilities at the Imperial College Geotechnics
Laboratory, presenting a new temperaturecontrolled
triaxial apparatus for saturated soils,
its thermal performance, the calibration of its
components for the effects of temperature and
the strategies for measuring thermal strains. It
also describes the calibration and compares
the use of the single needle and the dual-probe
heat-pulse needle techniques for the measurement
of thermal properties of soil. The second
part of the project focuses on the characterisation
of several aspects of the THM behaviour
of London clay. Three different topics are considered:
the volume changes induced by temperature
cycles in reconstituted samples at
different stress levels and histories, the influence
of temperature cycles on the strength and
stiffness of reconstituted samples at different
stress levels and histories and the study of the
thermal properties of reconstituted and intact
London clay samples.
Numerical Study of Bentonite Buffer
Homogenisation upon Re-saturation
Researcher: Giulia Ghiadistri
Supervisors: Prof Lidija Zdravkovic, Prof David Potts, Dr
Katerina Tsiampousi
Sponsors: AMEC Foster Wheeler
A good understanding of the Thermo-Hydro-Mechanical-Chemical
(THMC) behaviour of highly
expansive clay, such as bentonite, is important
in some of the designs of the Engineered Barriers
Systems (EBS) for nuclear waste disposal.
In a Geological Disposal facility (GDF), coupled
interactions take place involving the EBS, the
host rock, the groundwater and the heat generated
by the radioactive waste.
One of the disposal concepts being considered
in the UK is to dispose of High Level Waste
(HLW) and Spent Fuel in containers surrounded
by a buffer material consisting of bentonite.
Bentonite’s capacity to swell provides a low
hydraulic conductivity barrier and protection of
the container.
The bentonite blocks or pellets will be emplaced
in an unsaturated state. This bentonite
then undergoes a process of re-saturation from
the groundwater from host formation. Studying
bentonite resaturation is a challenging
task, as it involves swelling upon wetting from
groundwater in the host formation and shrinkage
induced by heat coming from the energy
generated by the nuclear waste in the container.
Nevertheless, it is important to build confidence
in the long-term behaviour of the EBS.
For the investigation of the behavior of unsaturated
soils, commonly adopted constitutive models
are the Barcelona Basic Model (BBM) and the
Barcelona Expansive Model (BExM): within this
project, the aim is to develop a BExM-type model
aimed at studying bentonite re-saturation.
57 http://www.imperial.ac.uk/nuclear-engineering