Author: Fanny Strandström
Supervisor: Mikael Rinne
Advisor: Miika Kalliokari
Collaborative partner: Kalliosuunnittelu Rockplan Oy ltd
Sealing the tunnels against water inflow is an important step in tunnel construction projects. Finland and Sweden have similar geologies, that is why it is interesting to observe that the grouting design approaches differ from each other significantly. This thesis is a comparative study where the differences in grouting design and execution of grouting in Finland and Sweden are mapped. A case study is also conducted in this thesis.
In Finnish civil projects the grouting design is based on experiences and empirical knowledge, while in Sweden, a much more theoretical approach is applied when drafting the grouting design. The reasons behind these differences are discussed throughout the thesis. The view in Finland is that the geology is difficult to precisely predict as the rock’s properties measured in the pre-investigation phase are point specific. For this reason, a design that can be self-adjusting and adapted to the actual site conditions is important. This is obtained by conducting measurements at probe-holes and grouting holes prior to the actual grouting activity and based on the results of the on-site measurements, the design parameters are updated and evaluated by the designer. In Sweden, the view is that the best grouting results are obtained by adapting analytical equations to the design. The expected apertures are calculated analytically based on the measured transmissivities and conductivities in the pre-investigation phase. Then, the penetration lengths and the necessary grouting times are calculated with the equations presented in chapter 3. The different design approaches lead to very different grouting parameters in regards of both pressure and pumped volumes.
In the case study the extensions of the capitol city subway lines in Finland and Sweden are compared and the grouting of the nuclear repositories’ test tunnels in ONKALO, Posiva and the TASS tunnel in Äspö are compared.
The differences in the grouting design and execution of the grouting design in the West metro subway extension in Finland and Blue Line project in Sweden were significant. In the West metro project higher pressures were used and the maximum allowed grouting volumes were up to 26 times larger compared to the Blue line project. It was also interesting to see that more pre-investigations were done in the West metro project compared to the Blue line project, even though the Blue line project used the theoretical approach in the grouting design.
The repositories differences in grouting design were minor. In Finland freshwater grouting is conducted prior to the actual grouting to clean the fractures while in Sweden, it is unknown if this additional step is being taken.
Keywords: Grouting, Länsimetro, West metro, Blue line, Repository, Posiva, SKB, Tunnelling, Hydrogeology