Tunnels represent significant investments and remain in service for extended periods of time, sometime beyond their intended service life. Their structural, civil and functional systems deteriorate at accelerated levels because of the harsh tunnel environment, in particular water infiltration.
Ideally, the maintenance strategies of a tunnel facility should strike a balance between preventive and on-demand/curative maintenance. When 70 to 80% of maintenance activities are performed under a preventative maintenance approach, it is considered to be good practice.
Refurbishment programs are undertaken when the tunnel is near the end of its useful life or when structural changes or repairs are needed (new regulations, evolution of traffic, fire damages, changing geologic conditions, etc).
Whether it is maintenance work or heavier work, interventions in tunnels bring additional challenges due to the difficult tunnel environment.
Working under reduced light conditions, difficult or limited access and egress, with the potential for exposure to air contaminants and the hazards of fire and explosion, underground construction workers face many dangers. Appropriate risk control plans must be in place and strictly enforced.
For both tunnel users and workers, total closure of all tunnel tubes during refurbishment/upgrading obviously provides a much higher level of safety. But in some cases, the work has to be carried out while the tunnel remains in service, with partial traffic closures, which requires a specific traffic management plan.
With trucks carrying rock and spoil out of the tunnel, working in the tunnel can become difficult due to airborne particles such as silica dust and diesel particulates.
Protective equipment such as breathing apparatus should therefore be provided for the site crew. This equipment will reduce worker mobility and increase fatigue, which in itself presents additional challenges.
Tunnel work involves managing the delivery and storage of equipment, tools and vehicles in a small and confined space.
This requires even greater coordination than on other sites, to ensure that products are delivered just-in-time and properly stored on-site.
With more than 70 years of experience in the repair and reinforcement of tunnels and underground facilities, you can confidently include us in the early stages of your refurbishment or upgrading project: we will advise on the most suitable techniques, provide assistance with structural analysis, condition assessment and solution design, and help you to take into account all the aspects and constraints of the project.
Freyssinet can operate as a general contractor or subcontractor to maintain, repair, strengthen, refurbish and protect tunnels.
It should be noted that we have access to photogrammetry programs developed by Sixense, a company in the group, to make a precise inventory of the defects in the structure, locate and prioritise the areas to be repaired, derive the corresponding quantities and prepare the repair work drawings.
We offer our services for large-scale repair programs of masonry and concrete railway and roadway tunnels involving substantial engineering input, extended durations or special conditions such as emergency interventions, work under traffic, difficult access, etc.
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