May 18, 2024
Global Tunnel Boring Machines

Tunnel Boring Machines: Underground Infrastructure Development

History and Evolution

The first tunnel boring machines were developed in the mid-19th century as a safer alternative to traditional drill and blast methods. One of the earliest ones was built in 1854 by American engineer Daniel Hall. It was able to excavate soil using a rotating cutting wheel on its nose. This kickstarted the development of increasingly sophisticated TBMs over the next few decades.

By the early 20th century, TBMs were being used extensively in Europe for metro and water Global Tunnel Boring Machine construction projects. Two significant innovations were hard rock TBMs equipped with disc cutters and shield TBMs that provided ground support as they excavated. During this period, TBM technology advanced rapidly with larger drive power and cutting tools able to excavate through harder rock and soils.

After World War 2, there was a surge in mega infrastructure projects requiring tunnels. This presented major engineering challenges and opportunities to develop even more powerful TBMs. Innovations included bi-directional machines that excavated tunnels from both ends to meet in the middle. The 1970s saw the widespread adoption of computer controls and new cutterhead designs that increased machine performance.

Modern TBM Design Features and Performance Capabilities

Today’s TBMs come in a variety of configurations depending on the geology, but they all incorporate the latest technological advancements. The cutterhead at the front is fitted with an array of disc cutters or teeth that grind through soil and rock using huge torque and thrust. Behind this is the main body which houses the cutting tools, conveyor system and segments for ground support. State-of-the-art steering, guidance and muck removal systems have made TBMs highly productive tunneling assets.

The largest hard rock TBMs now have cutterheads up to 14 meters in diameter driven by motors producing over 10,000 horsepower. They can excavate through rock at rates exceeding 100 meters per week. Soft ground and slurry TBMs commonly used for metro, water and sewage tunnels routinely operate at 25-40 meters per week. The world depth record for a TBM was set at 2,610 meters below ground during the Gotthard Base Tunnel project in Switzerland.

Global Deployment of Tunnel Boring Machines

Over the past few decades, TBMs have been deployed in mega infrastructure projects all over the world. In Europe, iconic projects like the Channel Tunnel, Turin Metro, Paris Sewers and Gotthard Base Tunnel utilised vast fleets of state-of-the-art rock and soft ground TBMs. In Asia, cities with intensive metro development like Tokyo, Beijing, Taipei and Singapore saw TBMs boring over 1000km of tunnels by the early 2000s.

North American cities also leveraged TBM technology heavily for new subways, road tunnels and water conduits. Projects included Boston’s Big Dig, San Francisco BART expansion and the Los Angeles Metro system. Tunnels under rivers like the Hudson and Potomac significantly expanded urban rail networks. In the past decade, developing nations like Brazil, India and Turkey have commenced ambitious metro tunneling drives utilizing cutting-edge tunneling machines. Recent examples include the Delhi and Mumbai Metro projects.

Advantages of TBM Tunneling Over Other Methods

Compared to traditional drill and blast tunnel excavation, Global Tunnel Boring Machine offers numerous advantages in terms of safety, schedule, quality and cost. It minimizes exposure of workers to excavation face hazards and eliminates the need for explosives. Large continuous faces can be excavated simultaneously in both directions allowing boring rates up to 10 times faster than drill and blast.

Modern EPB (Earth Pressure Balance) TBMs maintain a balanced pressure in the face by continually mixing excavated material to support the tunnel. This limits ground settlements and prevents surface disruptions. Segmental concrete lining installed by the TBM provides an immediate waterproof tunnel with precise internal dimensions. Overall, TBM tunneling yields significant productivity and quality benefits translating to lower project lifecycle costs.

Future Trends and Innovation

Looking ahead, there is still considerable potential to optimize TBM technology through data analytics, simulation modeling and new materials. Additive manufacturing and 3D printing applications are being investigated for on-site repairs and spare part production to minimize downtime. Integrated surveying and monitoring systems will provide real-time feedback to improve steering accuracy. Larger TBMs capable of excavating wider tunnel sections economically are on the horizon to meet growing infrastructure needs.

Automation and remote operations will enhance worker safety in hazardous tunnel environments. Cutting tools will evolve to efficiently handle increasingly abrasive and fractured rock conditions. Hybrid hard rock-soft ground TBMs may enable boring through highly variable ground strata with a single pass. Clearly, TBMs will remain indispensable for cost-effective, high-productivity underground construction across the globe well into the future.

1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it