The use of TBMs is the only solution for the planned Helsinki-Tallinn tunnel experts have concluded.
Speaking at the Tunnel Boring Seminar organised by Pöyry, A-Insinöörit and Finest Bay Area Development, Markku Oksanen, Pöyry’s Infra, Water and Environment Business Group, Northern Europe president Markku Oksanen said that TBMs are the only “reasonable solution” for the proposed railway tunnel between Helsinki and Tallinn below the Gulf of Finland.
Traditionally, the drill and blast method has been the main tunnelling technique used in Finland.
Oksanen said: “The construction period of this project will be exceptionally short. This is one reason for using TBM technique for a significant part of the tunnel, as it enables faster progress than drill and blast method. TBM method is also safe, and especially on the Estonian side, where the soil is soft and groundwater problem is obvious, TBM is the only reasonable solution.”
The conference also discussed the use of artificial islands to speed up the construction of the tunnels, with two artificial islands so that the TBMs can proceed in multiple directions simultaneously.
In addition, the islands could be used to store the approximately 80M.m² of rock and soil that is going to be excavated for the tunnel.
A-Insinöörit export director and chief customer officer Timo Saanio said: “Helsinki-Tallinn tunnel is super interesting. The project is massive. We are connecting two countries closely together with the world’s longest undersea railway tunnel. Even though we have contributed to hundreds of underground structures before, this rises in many ways above others.
“The project is already raising interest around the world, as we see from the fact that the world’s top experts came to our seminar in Finland. What also makes this project special is the way we have run it from the beginning, being open-minded towards new ways of doing things.”
In May, a task force established to examine how to proceed with Helsinki-Tallinn tunnel reported back saying that new technologies and private sector involvement were needed for the project to progress.