2009 Report to Government on National Research and

few millimetres <strong>to</strong> tens of metres. They are generally formed as a result of
stresses applied <strong>to</strong> the rocks over geological time and their presence has a
significant effect on the geomechanical behaviour of the rock mass. To
understand the influence of these features fully it is considered that their
genesis should be unders<strong>to</strong>od. This is an area where site specific research
in the related fields of structural geology and rock mechanics would aid site
characterisation.
• The current distribution of stress within a rock mass is influenced by the
distribution, frequency and nature of the fractures present. Research in<strong>to</strong> the
relationship between fracture distribution and stress fields would aid in site
characterisation.
• Understanding the controls on identification and description of the
distribution of permeability in low-permeability rock units will be essential <strong>to</strong>
the characterisation of a potential GDF site.
• Research will be required in relation <strong>to</strong> understanding, in a fractured hard
rock, the connectivity and transmissivity of the network of fractures. In
addition research will be required in<strong>to</strong> any lithological and structural controls
on permeability distribution.
• Water passing through fractures in the rock mass is influenced by the
surface characteristics of the fracture surfaces. This will change depending
upon the in situ stress conditions. Research <strong>to</strong> understand the influence of
fracture wall roughness and in situ stress would be useful in the
characterisation process.
• Geophysical techniques will be employed during site characterisation <strong>to</strong>
understand the spatial variability both horizontally and vertically of the
various rock types and geological structures at any proposed site. This will
assist in understanding groundwater movement and an initial assessment of
rock mass and material parameters. 3D seismic investigation and other
geophysical techniques have been developed for mine planning over recent
years as highlighted at the RWIN Meeting in April <strong>2009</strong> (CoRWM doc. 2619).
It is considered that research in<strong>to</strong> the use of these techniques in relation <strong>to</strong>
possible GDF sites could inform geosphere characterisation and assist in
GDF layout and the design.
Microbiology
A.95 Biological, and particularly microbiological processes, have considerable
potential <strong>to</strong> influence performance of a GDF, for example through accelerated
degradation of e.g. cemented wastes (Avaim et al., 2004; Rogers et al., 2003),
corrosion of steel containers (Landoulsi et al., 2008; Xu et al., 2008), perturbation
of biogeochemical conditions, generation of colloids and complexants (Gaona et
al., 2008; Glaus and Van Loon, 2008) and modification of flow paths (Suchomel
et al., 1998; Ross et al., 2007).
A.96 The microbial ecology of the GDF will be complex for several reasons. First, it is
very likely that there will be an indigenous microbial community in the host rock
formations. This will be perturbed during construction and exposed <strong>to</strong> a very
diverse array of immigrants, many of which could potentially colonise. On closure
and resaturation, when anaerobic conditions are reinstated, the new community
will evolve further. Evolution in community composition and genomes will be
driven by fac<strong>to</strong>rs such as pH (potentially very high), temperature, the radiation
CoRWM Document 2543, Oc<strong>to</strong>ber <strong>2009</strong> Page 123 of 151