First tunnel boring machine begins work on new Metro Line 7
The machine is almost the same length as the Entel Tower and will be used in the extension to Renca.
A tunnel boring machine (TBM) has begun to operate for the first time in the history of Santiago’s Metro. The machine will help excavate 6.6 kilometers of the underground train system’s future Line 7.
This is an unprecedented milestone, as this type of technology has never been used before in the construction of a Metro line in Chile. As explained by Transport Minister Juan Carlos Muñoz, the TBM will be used in Renca, and not on the rest of Line 7. This is because the machine adapts to the municipality’s soil type, and thus reduces the impact on the work’s exterior.
How does the new Line 7 tunnel boring machine work?
The tunnel boring machine installs each ring of seven voussoirs, which continuously pass through the machine while it advances with the excavation. Each ring of voussoirs has an outer diameter of 9.5 meters, is 32 centimeters thick, 1.7 meters deep and weighs almost 40 tons.
The earth that is extracted passes through a conveyor belt to the end of the tunnel section, accumulating in a single point. This produces less impact on the surface and on people.
The facilities of the voussoir plant are located adjacent to the terminal station in Renca. They have a total area of 5.7 hectares (14 acres), which is divided between the voussoir manufacturing and collection areas.
It will manufacture on average 70 voussoirs (10 rings) per day. It will produce 26,000 voussoir units in total, which will be installed by the tunnel boring machine between 2024 and 2026.
Facts and figures of the new Line 7 tunnel boring machine
- It was brought in parts by ship from the port of Shanghai, China, to the port of San Antonio, Chile.
- Final assembly took three months, and was supervised by technicians from China.
- The road transfer was carried out at night and at different times, due to the large size of the components that were escorted by Carabineros (Uniformed police service).
- For the first time in Chile, it will be used for the construction of a Metro line.
- TBMs have been used in the construction of subway tunnels around the world, including Barcelona (Spain), Paris (France), London (United Kingdom), Sydney (Australia), Tokyo (Japan), Quito (Ecuador) and Lima (Peru).
- It measures 110 meters in length. It is almost the same size as the Entel Tower, if placed side by side. It is only 17 meters smaller than the 127-meter tower.
- It is operated in shifts by 25 people who have been specially trained for the task. All are from the mining sector.
- It has a rotating cutting wheel driven by hydraulic motors with a diameter of 9.8 meters and a weight of 190 tons.
