Tunneling machines, also known as tunnel boring machines (TBMs), play a crucial role in the construction of underground tunnels. These massive machines are used to excavate tunnels by drilling through various types of rock and soil. They have revolutionized tunnel construction by providing a safer, more efficient, and faster method of digging underground passages.
But how deep can these tunneling machines actually go? The answer to this question depends on various factors, including the type of TBM being used and the geological conditions of the area.
Standard TBMs, commonly used for shallow tunneling projects, typically have a maximum drilling depth of around 60 meters (200 feet). These machines are equipped with a rotating cutterhead that has cutting tools or discs. As the cutterhead rotates, the cutting tools chip away the rock or soil in front of it, creating a tunnel.
However, for projects that require tunneling at greater depths, specialized TBMs known as deep-level TBMs are utilized. These machines often incorporate advanced features to withstand the immense pressures and challenging geological conditions encountered at deeper levels. Deep-level TBMs can dig tunnels as deep as 6 kilometers (3.7 miles) or more.
To achieve such depths, deep-level TBMs may employ additional technologies such as hydraulic systems to balance the external pressure, advanced cooling systems to manage heat generated during drilling, and shielded or pressurized cutterheads to ensure stability and safety.
One notable example illustrating the capabilities of deep-level TBMs is the Gotthard Base Tunnel in Switzerland, the world’s longest railway tunnel. Completed in 2016, this tunnel reaches depths of up to 2.3 kilometers (1.4 miles) beneath the Swiss Alps. To excavate the tunnel, several state-of-the-art TBMs were deployed, with the deepest point being approximately 750 meters (2,460 feet) below the surface.
However, it’s worth noting that drilling deeper tunnels using TBMs becomes increasingly challenging due to higher pressures, temperature variations, and the need for proper ventilation and safety measures. As a result, projects involving extremely deep tunnels are relatively rare and require thorough planning, engineering expertise, and specialized equipment.
Tunnel boring machines (TBMs) can excavate to significant depths. 21st-century rock TBMs can excavate over 700 meters per week, while soil tunneling machines can exceed 200 meters per week. The tunneling speed generally declines as the tunnel size increases. TBMs are capable of digging full-face tunnels underground in a single mechanical operation by drilling. They work in a variety of terrains, from sedimentary and volcanic rock to sandy or clay soils. The rates of tunneling can reach up to 15 km/year and sometimes even more[1][2][4].
In summary, while standard TBMs are suitable for shallow tunneling projects, deep-level TBMs are specifically designed to dig tunnels at greater depths, reaching depths of several kilometers. These machines have enabled the construction of remarkable infrastructure projects worldwide, making it possible to navigate through mountains, rivers, and even beneath cities.
Citations:
[1] https://en.wikipedia.org/wiki/Tunnel_boring_machine
[2] https://www.ferrovial.com/en/stem/tunnel-boring-machine/
[3] https://youtube.com/watch?v=MuYdnzcQXhk
[4] https://www.sciencedirect.com/topics/engineering/tunnel-boring-machine
[5] https://youtube.com/watch?v=z38JIqGDZVU
