Since August Adval has been working on the E18 Kolsilan kallionunneli (Kolsila Road Tunnel) in Hamina, Finland. The twin-tube road tunnel will have an overall length 304 m and a cross section 122,5 m². Combined volume of excavation is about 37.200 m³. The works consist of drilling, blasting, reinforcing, grouting, bolting, drainage installation works and another collateral works. The works have to be executed very carefully as the site is located in an urban area and the regulations and requirements concerning limitations on the noise, vibrations etc are very high.
The project comprises the construction of very specific inner lining structure: a thin, suspended shell structure. This system consists of so called collision elements. Those are precast walls placed on both sides of the road. After that the suspended shell structure will be installed in the tunnel crown between the walls. The shell is formed by a combination of a tunnel sealing membrane, suspended with a certain distance to the rock, and a 100 mm thick shotcrete lining that is applied in a next step towards this membrane.
Before the start of excavation Adval already executed the strengthening of the face using bolting and grouting.
