Innovations

The fire performance of tunnel structures is typically specified through nominal fire resistance, where structural performance is evaluated considering a standardized heating curve for a prescribed number of minutes. Often the fire performance evaluation is further simplified by only considering limits to the temperature increase inside the concrete, hereby completely neglecting the redundancy in the structural system. Structural fire engineering calculations explicitly account for these redundancies in fire resistance evaluation, enabling optimized fire protection and potential cost reduction. There is however a second and more important benefit of structural fire engineering. Real fires do not only have a heating regime, such as those considered in the nominal fire resistance evaluations, but also a cooling phase. The cooling phase can cause significant changes in tunnel behavior, such as large permanent deformations, extensive cracking on the unexposed (cold) side, and in extreme cases, even structural collapse hours after the fire is extinguished. Structural fire engineering calculations allow to evaluate the tunnel’s fire performance during all phases of the fire. Thus, it is possible to design tunnels for burnout performance (meaning that the tunnel is designed to also survive the cooling phase), and even to design the tunnel to limit the post-fire damage and downtime. Ultimately, structural fire engineering calculations can help optimize fire protection strategies, balancing initial fire protection investments with potential damage costs, thereby reducing the lifetime cost of fire for tunnel structures.

In tunneling projects, it is estimated that 60% to 70% of the embodied carbon is associated with the concrete linings of shafts and tunnels. Therefore, optimizing these linings is essential for reducing the overall carbon emissions of such projects. One effective solution involves using high-performance steel fibers as reinforcement, which can replace traditional steel rebar and allow for a reduction in the thickness of concrete elements, either fully or partially. This presentation will focus on two specific applications where steel fibers can lead to significant reductions in embodied carbon: precast segmental linings and cut-and-cover tunnel cast-in-place linings. We will provide an overview of the state-of-the-art in steel fiber concrete and highlight several case studies where the use of steel fibers has successfully contributed to lowering the embodied carbon in concrete linings.

Autostrade per l’Italia, with its engineering firms TECNE, has developed an approach to refurbish existing tunnels named Tunnel Renewal Strategy (“TRS”). TRS aims to achieve service life’s renovation through 8 different relining treatments. Over the last three years the design of the solutions has been developed and studied and key factors, leading to success or to the need for further improvements, have been identified. Beyond this, the method for selecting the right treatment among the solutions is driven by a multicriteria analysis including a supporting decision tool, based on asset management best practice, to account for others then technical aspects. Sound decision making is becoming part of the asset management strategy of the Organization, involving the Client and the Contractor in a continuous exchange of insights about budget limits, service life of the solutions and needed technologies to minimize the impact and keep serviceability of a very busy infrastructures.

HINFRA has developed a technology named ETLR (Extruded Tunnel Lining Regeneration), with the scope to build new linings for existing tunnels adopting an ultrafast horizontal slip-forming. The ETRL processing train is a machinery consisting of several modular units, each solving a specific function. The incremental industrialization of set of operations, typically the demolition, the surface preparation, and the new lining phases, combined with the performances of the special concrete, allow to target productivity rates far from the traditional methods in use in the industry. The engineered Fiber-Reinforced Concrete (FRC) is characterized by high early-age strength parameters, that allow a rapid slip-form at a predetermined time. A solid step into the technology implementation has consisted in the construction of a real scale extrusion facility, where the main components of the ETLR train are designed, produced, and tested. The solution was then transferred to pilot projects starting from 2023.

This workshop will discuss the growing appetite and opportunities for innovation in tunnel asset management. In particular computer vision based techniques enabling the automated capture of tunnel inspection imagery and data, advancements in data visualisation and dashboarding and the use of AI and machine learning for defect detection and inventorying. Benefits, blockers and lessons learnt from the development and deployment of innovative technology across tunnel projects in construction and under management across the world shall be discussed.

Facing the complexities of tunnel longevity due to environmental impacts, thermal expansion and contraction, material wear, and aging, the precision in predicting how these stresses and movements affect tunnel structures is paramount. Tunnel joints are complex but vital components that accommodate tunnel movements while ensuring water tightness through a diverse and specific set of solutions and materials. This demands a specialized approach to investigate, analyze, engineer, and solve refurbishment challenges. This session introduces an innovative method that utilizes innovative diagnostic tools and dynamic modeling for residual lifetime determination of tunnel joints and integrates these insights into practical engineering solutions. We combine expert analysis with actionable refurbishment and modification strategies, crafted to meet the high standards of experienced tunnel engineers, asset owners, and asset managers. A significant part of this session will focus on helping participants recognize critical but often overlooked problems with underground tunnel joints. By demonstrating how to detect and address these issues before they lead to significant damage, we provide vital insights into maintaining the integrity of these essential components by addressing them as a system. By attending, you'll explore how to leverage these advanced techniques to enhance your existing knowledge and extend the operational life of critical infrastructure effectively. Join us to refine your expertise with the latest in tunnel assessment and intervention technologies.