Exploring the World of Tunnel Boring Machines Types Innovations and Leaders

Tunnel Boring Machines (TBMs) have transformed the way we build tunnels, making underground construction faster, safer, and more predictable. These complex machines combine mechanical engineering, geotechnical science, and automation to carve through soil and rock with precision. This post explores the different types of TBMs, their key components, recent innovations, and some of the largest machines in operation worldwide.

What Makes Tunnel Boring Machines Essential for Modern Tunneling

TBMs are designed to excavate tunnels continuously while supporting the tunnel face to prevent collapses. Unlike traditional drill-and-blast methods, TBMs offer steady progress and enhanced safety by controlling ground pressure and minimizing vibrations. Their operation depends on several performance metrics such as penetration rate, advance rate, cutterhead torque, total thrust, and face support pressure.

These machines integrate multiple systems:

• Cutterhead mechanics to break the ground

• Chamber pressure management to stabilize the tunnel face

• Segmental lining installation to support the tunnel walls

• Automation and monitoring for real-time control and safety

  
  

This integration allows TBMs to work in diverse ground conditions, from soft soils to hard rock.

Types of Tunnel Boring Machines

TBMs come in various designs tailored to specific ground conditions and project requirements. Understanding these types helps engineers select the right machine for each tunneling challenge.

• Earth Pressure Balance (EPB) TBMs

  
  

(Herrenknecht AG).

These advanced machines utilize the excavated soil, which is meticulously conditioned into a paste-like consistency, to maintain equilibrium and balance the pressure at the tunnel face during the excavation process. This technique is crucial in ensuring the structural integrity of the tunnel, as it allows for the effective management of the forces acting on the tunnel walls, thereby preventing any potential collapses.

Optimal Conditions for EPBs

EPBs are particularly well-suited for soft ground conditions characterized by low water content, such as clay or silt. These types of soil possess specific properties that allow the EPB to function effectively, as they can be easily manipulated into a paste that can fill voids and maintain pressure. The ability of the soil to retain moisture without becoming overly saturated is essential, as excessive water can lead to instability and complicate the excavation process.

Functionality of the Soil Plug

The soil plug created during the excavation serves as a critical support mechanism for the tunnel face. By effectively utilizing the conditioned soil, the plug provides necessary support that prevents the tunnel walls from collapsing under the weight of the surrounding earth. This support is especially vital in soft ground conditions where the risk of collapse is significantly heightened. The EPB machine continuously monitors the condition of the soil and adjusts the consistency of the paste as needed to ensure that the pressure remains balanced throughout the excavation process.

Advantages of Using EPB Machines

The use of Earth Pressure Balance machines offers numerous advantages in tunneling projects. One of the primary benefits is the ability to excavate in challenging ground conditions while minimizing the risk of surface settlement and other disturbances. Since the soil is retained and conditioned on-site, there is less need for extensive soil removal and disposal, which can be both costly and logistically complex. Moreover, the closed system of the EPB machine allows for better control over the excavation environment. This is particularly beneficial in urban areas where the proximity of buildings and infrastructure necessitates careful management of ground movements. The ability to maintain a stable tunnel face not only ensures safety but also enhances the overall efficiency of the tunneling operation.

Conclusion

In summary, Earth Pressure Balance machines play a vital role in modern tunneling operations, particularly in soft ground environments. By utilizing excavated soil conditioned into a paste, these machines effectively balance pressure at the tunnel face, ensuring stability and preventing collapse. The innovative use of a soil plug not only supports the tunnel structure but also contributes to the safety and efficiency of the excavation process. As technology continues to advance, the capabilities and applications of EPB machines are likely to expand, further enhancing their role in civil engineering and construction projects.

• Slurry Shield TBMs

  
  

  

Slurry shields play a crucial role in modern tunneling operations, particularly in challenging geological conditions. These specialized tunneling machines are designed to stabilize the tunnel face by utilizing a technique that involves injecting a mixture of bentonite or polymer slurry into the excavation chamber. This slurry serves multiple purposes, making it an essential component of the tunneling process.

Functionality of Slurry Shields

The primary function of the slurry is to provide support to the tunnel face, especially in situations where the surrounding soil is water-bearing or consists of loose, unconsolidated materials. In such environments, maintaining face stability is of utmost importance to prevent collapses that could jeopardize both the safety of the workers and the integrity of the tunnel being constructed. The injection of slurry creates a hydraulic pressure that counteracts the external earth and groundwater pressures, effectively stabilizing the tunnel face and allowing for safe excavation.

Composition of the Slurry

The slurry typically consists of bentonite clay or polymer solutions, both of which have unique properties that enhance their effectiveness in tunneling applications. Bentonite, a natural clay, is known for its ability to swell when mixed with water, forming a thick, viscous fluid that can effectively support the tunnel walls. On the other hand, polymer slurries are engineered to provide similar benefits but can offer improved performance in terms of viscosity and stability under varying conditions. The choice between bentonite and polymer often depends on specific project requirements, including soil conditions, environmental considerations, and cost-effectiveness.

Excavation Process

As the excavation progresses, the slurry plays a vital role in transporting the excavated material out of the tunnel. The slurry carries the soil and rock debris away from the working face, ensuring that the tunnel remains clear and that the excavation can continue without interruption. This continuous removal of material helps maintain a balanced pressure within the tunnel, which is critical for preventing inflow of water and soil from the surrounding ground.

Advantages of Using Slurry Shields

Using slurry shields offers several advantages over traditional tunneling methods. Firstly, the ability to maintain face stability in water-bearing soils significantly reduces the risk of tunnel collapse, which can lead to costly delays and safety hazards. Secondly, the method allows for the construction of tunnels in urban areas where surface disruption must be minimized. The use of slurry shields also enables deeper tunneling, as the hydraulic pressure can counteract greater external forces.

Conclusion

In summary, slurry shields represent a sophisticated and effective solution for tunneling in challenging ground conditions. By injecting bentonite or polymer slurry into the excavation chamber, these machines stabilize the tunnel face, facilitate the removal of excavated material, and maintain a crucial balance of pressure. This method is particularly suited for environments where traditional tunneling techniques would face significant challenges, making it an invaluable tool in the field of civil engineering and underground construction.

vation chamber. This method suits water-bearing soils and loose ground where face stability is critical. The slurry carries the excavated material out of the tunnel, maintaining pressure balance.

• Hard Rock TBMs

  
  

  

  Click and explore the Hard Rock TBM at TERRATEC

Equipped with advanced disc cutters, these Tunnel Boring Machines (TBMs) are specifically engineered to effectively fracture rock under conditions of high compression. The disc cutters, which are circular blades made from durable materials, rotate at high speeds to penetrate and break apart the tough geological formations encountered during tunneling. This innovative cutting mechanism is particularly well-suited for high unconfined compressive strength (UCS) formations, such as granite or basalt, which are known for their density and hardness.

Granite, a common type of hard rock, is composed mainly of quartz, feldspar, and mica, making it exceptionally resilient and challenging to excavate. Similarly, basalt, a volcanic rock, is formed from rapidly cooled lava and possesses a fine-grained texture that contributes to its strength. TBMs designed for these types of rock formations must be robust, incorporating high-quality materials and cutting-edge technologies to ensure efficient operation and longevity.

(Herrenknecht AG).

In addition to their powerful cutting capabilities, hard rock TBMs are typically equipped with a protective shield. This shield serves a dual purpose: it safeguards the machine itself from potential damage caused by falling debris and also provides critical protection for workers operating in close proximity to the tunneling operation. The shield acts as a barrier, preventing loose rock and other materials from collapsing into the tunnel space, thereby reducing the risk of accidents and injuries.

Moreover, the design of these TBMs often includes features such as hydraulic systems that aid in the stabilization of the machine while it operates in challenging geological conditions. The hydraulic systems also assist in the adjustment of the cutting head's position, allowing for precise control over the excavation process. Additionally, some TBMs are equipped with advanced monitoring systems that provide real-time data on the geological conditions being encountered, enabling operators to make informed decisions and adapt their strategies as needed.

Overall, the combination of disc cutters, a protective shield, and sophisticated engineering allows hard rock TBMs to efficiently and safely navigate through some of the most demanding subterranean environments, facilitating the construction of tunnels for transportation, utilities, and other infrastructure projects. This technological advancement not only enhances productivity but also contributes to the overall safety and effectiveness of tunneling operations in hard rock settings.

• Double Shield TBMs

(Herrenknecht AG).

Double Shield Tunnel Boring Machines (TBMs) represent a sophisticated and innovative approach to tunnel construction, merging the essential characteristics of both gripper and shield TBMs into a single, highly efficient system. This design enables these machines to perform two critical operations simultaneously: excavation of the tunnel and installation of the lining that supports the tunnel structure.

The dual functionality of Double Shield TBMs is particularly advantageous in various geological conditions, especially in stable rock formations, where the integrity of the surrounding material can be maintained during the boring process. The gripper system plays a pivotal role in this operation; it securely anchors the TBM to the tunnel walls, providing stability and preventing any unwanted movement that could compromise the excavation process. This anchoring mechanism is crucial in ensuring that the TBM can exert the necessary force to break through solid rock while maintaining a safe and controlled environment within the tunnel. In addition to the gripper system, the shield component of the Double Shield TBM serves as a protective barrier that safeguards the face of the tunnel from potential collapses or water ingress.

This shield not only enhances the safety of the operation but also allows for the continuous installation of precast concrete segments or other lining materials as the machine advances. As a result, the excavation and lining processes are seamlessly integrated, significantly reducing the time and labor typically required for tunnel construction. Moreover, Double Shield TBMs are designed to operate efficiently in a variety of conditions, making them versatile tools in the field of civil engineering. Their ability to adapt to different geological settings allows engineers to tackle complex projects that may involve varying ground conditions, such as transitioning from soft soil to hard rock.

The efficiency of Double Shield TBMs is further enhanced by their advanced technological features, which include automated systems for monitoring and controlling the excavation process, thus ensuring precision and reliability throughout the operation. Overall, the implementation of Double Shield TBMs has revolutionized the tunneling industry, enabling the completion of projects with greater speed and safety. Their unique design and functionality not only optimize the excavation and lining processes but also contribute to the overall sustainability of tunnel construction by minimizing the environmental impact associated with traditional methods.

• Mixshield TBMs

(Herrenknecht AG).

Mixshields are advanced hybrid tunneling machines that ingeniously integrate the technologies of Earth Pressure Balance (EPB) and slurry shield tunneling methods. This innovative design allows Mixshields to effectively navigate and adapt to a wide range of geological conditions, particularly in urban settings where soil types can change dramatically along the tunnel route.

The ability to seamlessly switch between EPB and slurry modes is crucial for maintaining face stability, which is essential for safe and efficient excavation. In EPB mode, these machines utilize the pressure of the excavated soil to support the tunnel face, which is particularly beneficial in cohesive soils. This mode helps to prevent ground settlement and maintain the integrity of the surrounding structures. Conversely, when conditions demand, Mixshields can transition to slurry mode, where a bentonite slurry is used to balance the pressure at the tunnel face, making it suitable for loose, water-saturated soils or when dealing with high groundwater levels.

The versatility of Mixshield TBMs not only enhances their operational efficiency but also significantly reduces the risks associated with tunneling in unpredictable ground conditions. By optimizing excavation techniques based on real-time assessments of the surrounding geology, these machines can minimize downtime and improve overall project timelines.

Furthermore, the deployment of Mixshields contributes to the sustainability of tunneling projects by reducing the environmental impact often associated with traditional excavation methods. Overall, Mixshield TBMs represent a significant advancement in tunneling technology, providing engineers and contractors with the tools necessary to tackle complex underground projects while ensuring safety and efficiency.

• AVN Machine

(Herrenknecht AG).

In modern trenchless construction and microtunnelling, the AVN machine has become one of the most reliable and versatile solutions for installing pipelines and tunnels with minimal surface disruption. Built by Herrenknecht, these slurry‑pressure‑balance systems are engineered to tackle challenging ground conditions while maintaining exceptional accuracy and safety during excavation.

An AVN machine is a fully enclosed microtunnelling system that uses slurry pressure to support the tunnel face, making it suitable for soft ground, mixed geology, gravel, and even rock. Its specialized cutterheads ranging from standard mixed‑ground wheels to disc‑cutter rock heads allow the machine to adapt seamlessly to changing ground conditions, while an integrated cone crusher ensures that stones and obstacles are reduced to a conveyable size. This technology enables precise excavation for pipe jacking from DN250 and segmental lining from DN3200, with diameters reaching up to 4.8 m. Supported by a remote‑controlled guidance system and laser‑accurate steering, AVN machines can achieve drive lengths exceeding 1,000 m, making them ideal for pipelines, sewers, utility corridors, and complex crossings under roads, rivers, and railways.

Overall, the AVN machine stands out as a true all‑rounder in trenchless tunnelling. Its ability to handle almost any geology, combined with high safety standards and long‑distance jacking capability, makes it an essential tool for modern underground construction projects seeking efficiency, precision, and minimal surface impact. Ref : [herrenknecht.com]

• Vertical Shaft Sinking Machines (VSM)

(Herrenknecht AG).

The Vertical Shaft Sinking Machine (VSM) developed by Herrenknecht is an innovative mechanized system designed for the fast, safe, and highly controlled construction of deep vertical shafts in challenging ground conditions. Suitable for soft ground, mixed soils, and rock up to 140 MPa, the VSM can excavate shafts with diameters from 4.5 to 18 meters and depths reaching up to 250 meters, even when working below high groundwater levels. Its key advantage is that excavation and shaft lining take place simultaneously, enabling sinking rates of up to 5 meters per shift while keeping all personnel safely at the surface through full remote control.

The VSM eliminates the need for groundwater lowering reducing settlement risks—and ensures high‑precision shaft geometry through continuous monitoring of the lowering process. Thanks to its modular design, it can be deployed efficiently in inner‑city or space‑restricted sites, with flexible arrangements of the separation plant, control container, and lowering units. This makes the VSM an ideal solution for constructing launch shafts, ventilation shafts, access points for tunnels, and deep utility structures, offering a modern alternative to conventional shaft sinking by significantly reducing concrete consumption, CO₂ emissions, and site impact. [Ref: herrenknecht.com]

• Rectangular TB

UGITEC

The UGITEC Rectangular TBM is a specialized non-circular tunnel boring machine designed to excavate rectangular, horseshoe‑shaped, and other custom tunnel profiles with high precision. Using UGITEC’s APORO rotary cutting technology, the machine maintains accurate geometry while cutting through hard ground and obstacles, making it suitable for complex urban projects.

UGITEC offers several types of rectangular TBMs, including the APORO Cutter TBM, the OHM‑type TBM with an eccentrically rotating three‑arm cutter capable of forming various rectangular or inward‑bowing shapes, and the MMST (Multi‑Micro Shield Tunneling) TBM, which constructs a large tunnel shell using multiple small TBMs before removing the inner soil.

These machines have been successfully used across Japan for major infrastructure works in Tokyo, Kyoto, Kanagawa, and other regions, with excavation dimensions ranging from 3–10 meters depending on the model. Their ability to deliver consistent profile control, navigate minimal overburden conditions, and cut complex geometries make UGITEC’s rectangular TBMs an advanced solution for underground passages, metro links, urban redevelopment utilities, and shallow‑cover tunnelling projects. [Ref: ugitec.co.jp]

• H&V(Horizontal & Vertical) TBM

rizontal & Vertical) TBM

UGITEC

The H&V (Horizontal & Vertical) TBM developed by UGITEC is a uniquely flexible tunnel boring machine designed for tunnelling routes that require both horizontal and vertical alignment changes. “H&V” stands for Horizontal variation and Vertical variation, and the system achieves this through independently controlled circular TBMs connected by a flexible joint, enabling the machine to adjust position during excavation.

Each TBM can also be disconnected underground when required, providing exceptional adaptability for complex urban or utility tunnel works. A key innovation is the cross‑articulation system, which allows spiral advancing movement, enabling the machine to shift from a top–bottom configuration to a right–left layout as alignment demands change.

UGITEC

The H&V TBM has been successfully deployed in major projects across Tokyo including the Minamidai Pipeline (1998) and Tachiai River Drainage Channel (2015) with excavation diameters ranging from 2.89 m to 11.79 m and drives exceeding 700 m. This combination of flexibility, articulation capability, and in‑ground reconfiguration makes the H&V TBM an ideal solution for tunnel routes requiring sharp geometric transitions or multi‑plane alignment control. [Ref: ugitec.co.jp]

Key Components of Tunnel Boring Machines

Understanding the main parts of TBMs reveals how these machines achieve their complex tasks:

• Cutterhead

The rotating front part equipped with cutting tools. Its design depends on the ground type. For example, disc cutters for rock or scrapers for soft soil.

• Thrust System

Hydraulic cylinders push the cutterhead forward, applying the force needed to break the ground.

• Shield

A cylindrical steel structure that supports the tunnel face and protects the machine and workers.

• Conveyor System

Transports excavated material from the cutterhead to the tunnel entrance or a disposal area.

• Segment Erector

Installs precast concrete segments to line the tunnel walls immediately after excavation.

• Control Cabin and Automation

Operators monitor and control the TBM using sensors and software that track pressure, torque, and other critical parameters.

Top TBM Manufacturers Worldwide

Country	Manufacturer	Specialties
Germany	Herrenknecht AG	Full-range TBMs (EPB, slurry, hard rock, mixshield); mega-diameter machines; automation suites
USA	Robbins Company	Hard rock TBMs, gripper and double shield systems, long-distance tunneling
China	China Railway Engineering Equipment Group (CREG)	Large-scale EPB and slurry TBMs; urban mega-shields; high-volume production
China	CRCHI (China Railway Construction Heavy Industry)	EPB and slurry TBMs; rapid deployment; strong presence in Asia
Japan	Kawasaki Heavy Industries	Precision slurry shields; robust bulkhead and seal systems. Note: Kawasaki Heavy Industries, Ltd. and Hitachi Zosen Corporation's TBM business were integrated into joint venture call UGITEC.
Japan	Hitachi Zosen (now Kanadevia Corporation)	Builder of Bertha (Seattle); large slurry TBMs; urban tunneling expertise. Note: Kawasaki Heavy Industries, Ltd. and Hitachi Zosen Corporation's TBM business were integrated into joint venture call UGITEC.
Australia/Asia	Terratec Ltd.	EPB, slurry, and micro-TBMs; custom designs for Asia-Pacific projects
France	NFM Technologies	EPB and slurry TBMs; specialized in metro and utility tunnels
UK	Tunneling Engineering Services (TES)	Micro-TBMs, pipe jacking systems, and custom tunneling equipment
China	CRTG (China Railway Tunnel Group)	TBM deployment and tunneling services; in-house machine customization
Germany	Bauer Maschinen GmbH	Vertical shaft boring and specialized tunneling equipment
Japan	Mitsubishi - JIM TECHNOLOGY (JIMT)	Slurry TBMs and shield machines for urban infrastructure
Italy	Seli Overseas S.p.A.	EPB and hard rock TBMs; metro and hydro projects
Singapore	Shanghai Tunnel Engineering Co. (STEC)	TBM manufacturing and tunneling services; large urban projects
Japan	UGITEC	Kawasaki Heavy Industries, Ltd. and Hitachi Zosen Corporation's TBM business were integrated into joint venture

🔧 What Sets These Suppliers Apart

• Herrenknecht leads in automation, digital integration, and mega-diameter machines.

• Robbins is known for durability and performance in hard rock environments.

• CREG and CRCHI dominate the Asian market with rapid production and deployment.

• Japanese firms like Kawasaki and Hitachi Zosen specialize in slurry shields for complex hydrogeology.

• Terratec and NFM offer flexible, project-specific designs for metro and utility tunnels.

Innovations Driving TBM Performance

Recent advances have improved TBM efficiency, safety, and adaptability:

• AI and Machine Learning

AI systems analyze sensor data to predict ground conditions and adjust machine parameters in real time. This reduces downtime and prevents damage.

• Improved Cutter Materials

New alloys and coatings extend cutter life, reducing maintenance frequency and costs.

• Enhanced Face Pressure Control

Advanced pressure management systems maintain optimal balance, especially in mixed ground conditions.

• Automation of Segment Installation

Robotic systems now assist in placing tunnel lining segments, speeding up construction and improving accuracy.

• Remote Monitoring and Diagnostics

Operators can oversee TBM performance from remote locations, allowing expert support and faster troubleshooting.

Largest Tunnel Boring Machines in the World

Some TBMs stand out for their sheer size and power, enabling massive infrastructure projects:

• Bertha (Seattle, USA)

Bertha is a slurry shield TBM with a diameter of 17.63 meters, built by Hitachi Zosen. It was used for the Alaskan Way Viaduct replacement tunnel, one of the largest urban tunneling projects in the United States.

Hitachi Zosen

• Herrenknecht Mega Shields

Herrenknecht, a leading TBM manufacturer, has produced several machines over 15 meters in diameter. These EPB and slurry TBMs have been deployed in China and Europe for metro and highway tunnels.

(Herrenknecht AG).

• Big Becky (Toronto, Canada)

This TBM has a diameter of 16.7 meters and was used for the Toronto Crosstown Light Rail Transit project. It is one of the largest EPB machines in North America.

These machines demonstrate how TBMs can handle complex urban environments and challenging geology while minimizing surface disruption.

Canadian Mining Journal

• Silvertown Tunnel TBM - Jil

The Silvertown Tunnel was constructed using the largest tunnel boring machine (TBM) ever used in the United Kingdom, specifically designed for this major river‑crossing project. The TBM—named “Jill”—had the following key dimensions:

TBM Diameter: 11.9 metres This cutterhead diameter made Jill the largest TBM ever deployed in the UK, capable of boring the twin‑bore Silvertown road tunnels beneath the River Thames.

(Herrenknecht AG).

Practical Considerations for TBM Projects

Selecting and operating a TBM requires careful planning:

• Ground Investigation

Detailed geotechnical surveys identify soil and rock types, groundwater conditions, and potential hazards.

• Machine Customization

TBMs are often custom-built or modified to suit specific ground conditions and tunnel dimensions.

• Logistics and Support

Transporting and assembling large TBMs requires coordination. Maintenance access and spoil removal systems must be planned.

• Safety Protocols

Continuous monitoring of pressure and machine health helps prevent accidents and delays.

Final Thoughts on Tunnel Boring Machines

TBMs have revolutionized tunnel construction by combining mechanical power with precise control systems. Their ability to work in diverse ground conditions and install tunnel linings simultaneously makes them indispensable for modern infrastructure projects. Innovations in AI, materials, and automation continue to improve their performance and reduce costs.

Tunneller to Tunnellers - Siv Brasha

Disclosure

Some information, images, product details, and technical descriptions shared on this blog are collected from official manufacturer and supplier websites. They are provided solely for informational and educational purposes. I do not claim ownership of any trademarks, product images, technical data, or brand materials.

While I aim to ensure accuracy, this blog should not be used as a substitute for official documentation or professional advice. Please always refer to the manufacturer or supplier for the most up‑to‑date and precise product information.

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