On October 8th, Obayashi Corporation, one of the four major construction companies in Japan, jointly announced with Toray Industries, Inc., Konoishi Corporation, and Chemical Construction Co., Ltd. that they had successfully developed a new carbon fiber sheet lamination process called "One-Bind Cross" and applied it to the reinforcement project of the Ryozan Tunnel on the Tohoku Expressway in Japan.
The new technology uses biaxial carbon fiber sheets, significantly simplifying the construction process for tunnel lining reinforcement and providing a brand-new solution for the renewal and maintenance of aging infrastructure. The development of the One-Bind Cross® process aims to fundamentally address the efficiency bottlenecks of traditional reinforcement methods.
Heavy-duty, biaxial carbon fiber sheet material
The technology employs double-axis carbon fiber sheets with a unit weight of 200g/m², an tensile strength of 2900 N/mm² or higher, and a static elastic modulus of 245±36 kN/mm². The use of the new high-weight sheets enables reinforcement operations to achieve the same reinforcing effect as traditional double-layer sheets with only a single layer of sheet.
Process Innovation
By setting impregnation holes at the fiber intersection points, it was ensured that the epoxy resin could fully penetrate the sheet material and the surface of the lining concrete. This significantly enhanced the bonding strength between the sheet material and the concrete surface, ensuring the reliability of the reinforcement effect.
Efficiency improvement: The optimization of construction processes has achieved remarkable results.
The One-Bind Cross® technology, in conjunction with other safeguard technologies developed simultaneously for this project, has achieved a comprehensive improvement in efficiency.
Significant reduction in production processes
The sheet laying operation has been reduced from the traditional two layers to one layer, and the process has been streamlined from the original 11 steps to 8 steps. At the same time, the sheet width has been increased from the traditional 500mm to 1000mm, effectively reducing the number of operations.
Vehicle-mounted working platform "Flap Lift"
"Flap Lift" provides a wide working platform (10.5 meters long) that can cover half of the cross-section of the tunnel. It can be unfolded and retracted on the base of a large truck and construction can be carried out by simply implementing one-way traffic control on the tunnel. The hydraulic system can position the platform at the optimal height and angle, facilitating the reinforcement of the tunnel lining. Workers can move freely on the platform, significantly enhancing work efficiency. When used in combination with One-Bind Cross®, it can further reduce the number of traffic control operations, doubling the construction efficiency.
"Pinant" Construction Environment Control System
"Pinant" is an environmental control system that can maintain optimal working conditions even in a high-humidity environment within a tunnel. Its tent-like structure closely adheres to the tunnel lining, preventing external air from entering the working area. By using circulating air, it maintains the required temperature and humidity for construction conditions.
This system helps prevent curing defects in the epoxy resin used with One-Bind Cross®, ensuring quality and preventing delays in progress due to downtime or rework.
Application example: Reinforcement project of Longsen Tunnel
The Ronsen Tunnel on the Tohoku Expressway in Japan has been in use since 1982. The concrete lining and the inspection walkways of the tunnel have all suffered damage and deterioration due to age-related wear and tear.
This reinforcement project not only repaired the concrete cracks, carried out section repair for the damaged parts, and injected into the voids, but also laid carbon fiber patches on the concrete surface to enhance the structural strength of the lining concrete. The successful implementation of this project provided reliable technical references and engineering demonstrations for a large number of similar aging tunnel reinforcement projects in Japan.
The R&D team stated that in the future, they will focus on further enhancing the strength of One-Bind Cross®, and plan to expand its application scope from tunnels to areas such as bridge pier seismic reinforcement, bridge deck beam reinforcement, and building structure seismic reinforcement.
As infrastructure in countries around the world generally enters the "aging" stage, this innovative technology not only provides a new solution for infrastructure maintenance in Japan, but also offers valuable technical references for similar challenges worldwide.