RD&D-Programme 2004 - SKB

Judgement with regard to long-term safety
Desirable
pH
Judged
acceptable
Uncertain
level
Not
acceptable
7 8 9 10 11 12 13
Figure 10-3. Judgement of accepted pH in leachates from material in deep repository with regard
to long-term safety.
Programme
The overall goal of the grouting research is to make sure that the necessary knowledge,
methods, grouting materials and equipment are available to deal with the sealing situations
that arise due to the special requirements that are made on the deep repository. Knowledge
concerning grouting has long been experience-based, while SKB’s programme is aimed at
acquiring a better scientific understanding of how the system consisting of rock, grout and
grouting technology works. Such knowledge is necessary to be able to control the grouting
process. SKB’s funding of doctoral projects is also aimed at ensuring that grouting will continue
to be a living discipline where new knowledge is acquired, disseminated and discussed in
broad circles to be used on a regular basis in civil engineering projects. SKB has also taken an
initiative to develop a training programme for grouters and design engineers. Swedish Rock
Engineering Research (SveBeFo) is responsible for the program.
The work of developing injection grouts that meet fundamental requirements and optimizing
them for use in the field is vital to the development of sealing systems. Our understanding of
grouting as a system needs to be improved, and SKB will continue to pursue independent and
joint projects in order to:
• Qualify cementitious grouting materials for sealing of large fractures and non-cementitious
materials for sealing of smaller fractures (< 100 µm) that produce leachates with a pH of
less than 11. This work is being pursued in cooperation with Posiva and Numo and includes
research and development in the laboratory and tests to check that it works in the field.
• Investigate and measure the mechanisms that control filtration stability, i.e. the ability of the
grout to pass constrictions without clogging. These properties are essential for penetration
and thereby also for the sealing results. The work, whose results to date have been published
in a licentiate report /10-6/, is being done as a doctoral project and is being co-financed with
SveBeFo, Elforsk and Cementa.
• Develop methods for characterizing rock and predicting grout penetration. The goal is to
further develop the methodology for characterization of the rock in such a manner that it
can be used to predict grout spread and grout consumption and thereby also to determine
a suitable grouting procedure. SKB is funding two postgraduate students for this work as
a continuation of previous doctoral projects.
10.1.4 Rock support
The durability of the underground facility during the construction and operating phases is
determined by, among other things, the technical lifetime of the different parts of the facility.
The need for rock support is a part of the design-basis information gathered for the underground
part of the facility. This need is dependent on such factors as the properties of the rock
mass, loads in the form of rock stresses and the geometry of the openings. The need for rock
support is also dependent on the performance and technical lifetime of the openings, as well
as maintenance and environmental requirements. The main rock support methods that will be
used are conventional support elements such as rock bolts, shotcrete and wire mesh.
118 RD&D-Programme 2004