In TBM (Tunnel Boring Machine) tunneling operations, excavation efficiency depends on more than just the machine’s capabilities. Behind every meter of progress lies a system of closely coordinated technical solutions designed to sustain the excavation process, manage geological conditions, and ensure the quality of the tunnel lining.
A critical step in this process is annulus grouting—filling the void created between the excavated ground surface and the segmental tunnel lining.
Leveraging extensive expertise in underground construction, MC Underground (MCU) has developed annulus grouting solutions for TBMs that incorporate EFC (Earth Friendly Concrete) technology, aiming to strike a balance between technical performance and reduced environmental impact.
Annular Gap – A Critical Issue in TBM Tunnel Construction
During TBM tunneling, the excavation diameter of the cutterhead exceeds the outer diameter of the segmental tunnel lining installed behind the machine. This difference creates a void between the lining and the surrounding ground, known as the annular gap.
This void must be promptly filled with a suitable grout.
Backfill grout serves to fill the space behind the segments, helping to provide uniform support for the tunnel lining, stabilize the surrounding ground, and assist in controlling deformation and surface settlement during construction.
This is why backfill grout constitutes a critical component of modern TBM tunneling technology.
What requirements must TBM backfill grout meet?
Tunnel construction conditions vary significantly depending on geology, TBM type, segment design, excavation speed, and specific project requirements. Consequently, backfill grout serves a purpose far beyond merely “filling the void.”
A suitable grout system must be designed to meet various technical specifications, such as:
- Stable pumpability and workability
- Effective annular gap filling
- Controlled setting time
- Appropriate strength development
- Creation of a stable support layer for the tunnel lining, etc.
The ability to control the backfilling process is particularly critical for projects such as metros, urban railways, or underground structures built in densely populated urban areas.
This is also an area where TBM’s chemical and technology play an increasingly important role in optimizing grout performance based on the specific conditions of each project.
EFC – Earth Friendly Concrete: A breakthrough in MCU’s pumpable backfill grout technology.
Beyond technical performance, the construction and underground engineering sectors are increasingly prioritizing resource optimization and the reduction of the environmental impact of materials.
In line with this approach, MCU utilizes EFC (Earth Friendly Concrete) technology to develop annular gap grouting solutions for Tunnel Boring Machines (TBMs).
This technology focuses on optimizing material composition and incorporating suitable alternative raw materials, thereby helping to minimize environmental impact while meeting the rigorous technical requirements of tunneling operations.
The significance of EFC extends beyond mere environmental considerations. For underground projects, a solution is truly valuable only when sustainability goals are balanced with construction efficiency, structural stability, and project-specific technical requirements.
This is precisely the approach MCU takes in developing new generations of materials for TBM technology.
Annular gap grouting solution system from MC Underground
Each TBM project presents a unique set of requirements. Consequently, MCU develops annulus/backfill grout systems in various configurations to suit specific construction conditions and technical specifications.
These solutions can be formulated as either single-component (1K/1C) or two-component (2K/2C) systems, with properties such as pumpability, working time, setting behavior, and strength development tailored to project needs.
In addition to traditional grout systems, MCU develops specialized material technologies for unique geological conditions where standard solutions may prove insufficient to address the engineering challenges.
This approach allows TBM backfill grout to function as an integral part of a project-specific engineering solution, rather than merely serving as a standalone material supply.
From technical efficiency to a focus on reducing environmental impact
Underground infrastructure projects increasingly face the dual challenge of achieving higher technical performance while upholding greater environmental responsibility.
The application of EFC technology in the development of backfill grouts reflects MCU’s commitment to striking a balance between these two objectives.
From material optimization and constructability to meeting the technical requirements of tunnel structures, the goal is not merely to create a high-performance grout system, but to deliver underground infrastructure solutions that align with future trends in sustainable construction.
MCU – Integrated solution system for TBM tunneling technology
Annulus grout is just one component of MC Underground’s ecosystem of solutions for TBM tunneling. MCU develops integrated solutions to support critical stages of TBM operations:
- Soil conditioning
- Annulus grouts
- Tail sealing materials
- Bearing lubrication and sealing
- Injection and waterproofing systems,…
Leveraging its expertise in materials and specialty chemicals, combined with extensive experience in underground construction technology, MCU aims to partner with project owners, consultants, and contractors to address the specific technical challenges of each project.
MC Underground (MCU) – Global Partner for Underground Construction Solutions
MC Underground (MCU) is a division of the MC-Bauchemie Group—a global leader in construction chemicals with over 60 years of experience, operations in more than 50 countries, and a workforce of over 3,500 people worldwide.
MCU provides specialized chemical solutions tailored to the tunneling and mining industries. Our team of international experts partners with clients throughout the entire project lifecycle, offering everything from technical consulting, research and innovation, and high-quality product supply to on-site support services.
