Fibre reinforcement can reduce up to 40% of tunnel lining costs

Fibre reinforcement can reduce up to 40% of tunnel lining costs

Feb 10, 2016  Civil engineering 

Fibre reinforcement can reduce up to 40% of tunnel lining costs
(Photo by: Ramboll)

New international guidelines suggest that the use of fibre reinforcement could cut 40% of costs compared to more traditional lining methods. Furthermore, fibre reinforcement offers a more sustainable and time-saving alternative.

New guidelines for fibre reinforcement in tunnels can change deep-rooted traditions within tunnel projects. The guidelines, which is created by experts from the International Tunnel Association (ITA) spearheaded by Alun Thomas, head of Ramboll’s tunnel division, documents that using fibres instead of traditional reinforcement will save you up to 40 percent of the costs of tunnel lining.

At the same time, the fibres have a number of other qualities that save time as well as steel – thus significantly reducing CO2 emissions.

But in spite of obvious and significant advantages, the majority of tunnel constructions worldwide are lined with concrete segments using traditional bar reinforcement:

- Traditions and a lack of a universally accepted design standard keep the industry from embracing fibre reinforcement as the preferred solution. The reason is partly that clients wish to use a technology that is thoroughly tested and since we are talking about tunnels with a lifespan of about 100 – 120 years, this is very understandable, says Alun Thomas, who, besides from being head of Ramboll’s Tunnel Department, was chairman of ITA’s expert group (ITAtech) while the guidelines were created.  

The new guidelines are the result of two years of work and it provide something that has been lacking on the market for decades: An internationally respected guide that designers and contractors can refer to when they pitch the idea of using fibre reinforcement to a client. 

Less time, steel, and CO2

Fibre reinforcement is the more sustainable solution, as it will typically halve the amount of CO2-emissions compared to the production of traditional reinforcement. At the same time you can do without the traditional reinforcement and thereby skip an entire step in the work process, which in turn saves a lot of time.

- The advantages of using fibre reinforcement are significant, and I strongly recommend considering this material. Traditional reinforcement bars can be totally or partially replaced with fibre reinforcement without compromising the structures’ ability to withstand heavy loads, Alun Thomas explains.

Better resistance

Furthermore, the guidelines explain that fibre reinforced concrete segments perform better in many other aspects, such as corrosion.

  • If chloride induced corrosion is present in a traditionally reinforced concrete segment, the reinforcement bars’ volume will increase, which can cause the concrete to crack. This can result in enormous repair costs, says Alun Thomas and continues:
  • If, however, fibre reinforced segments are subject to chloride induced corrosion, the fibres inside the concrete are not affected in this way and the structure will remain intact. 

At the same time, the surfaces and corners of fibre reinforcement are more resistant to handling and transportation, which often cause damage to the segments and installation. The reason is that the fibre reinforcement is evenly distributed in the concrete.

In the guidelines you can read about the following advantages of using fibres:

  • A decrease in the tunnel lining costs of up to 40 %
  • How to replace all steel bars with either steel or macro synthetic fibres
  • Reductions of 50% or more in  the embodied CO2 
  • Increased resistance to chloride induced corrosion
  • Corners and surfaces with increased resistance to transport and handling
  • Fewer steps in the work process, resulting in less time spent and less space needed at the segment factory

Via Ramboll
Image,video ©: Ramboll