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Green innovations at the Brenner Base Tunnel

20 December 2015
the Brenner Base Tunnel
In the Swiftly Green project additional knowledge supporting the greening of TEN-T Core Network Corridors are added by the implementation of Best Practice Cases. One of these is the investigation of green innovations applied at the Brenner Base Tunnel (BBT).

The Swiftly Green project is now ending and part of the results from the BBT best practice case was presented at the final conference in November 2015. We have talked with the two project leaders for BBT best-practice case, Tobias Cordes and Stefano Casale at BBT-SE.

The general aim of work on the BBT best practice cases was to enhance the sustainability of the tunnel infrastructure. For this purpose green innovations implemented at the BBT were chosen, investigated and promoted within the work of Swiftly Green.

tobias_cordes.jpgThe greening measures can be summarized in three subjects; Recycling of tunnel spoil, Low-level CO2 concrete and shotcrete, and Geothermal energy exploitation.

“This selection, out of other important subjects, was done to receive solid and effective greening measures, which guarantee a sufficient transferability to other infrastructure projects”, says Tobias Cordes.

Of course there have been some challenges in this study.

“The planning of a sustainable infrastructure is important but the implementation of green innovations in the construction phase is a real challenge. For a greener solution all interconnected processes and all dependencies on site must be investigated and solved,” says Tobias Cordes

Important result from the project

The BBT best practice cases in the Swiftly Green project have made some interesting result in each three of the determined subjects.

Recycling of tunnel spoil

At BBT site Wolf the concrete aggregates used for producing shotcrete and construction concrete have been one hundred per cent sourced from the processed tunnel spoil. On this site the transport of concrete aggregates on public roads was totally avoided and the area of landfills decreased. Evaluations by life cycle assessments (LCA’s) were realised and give detailed insight in dependencies and quantify the reduction of the environmental pollution.

“It shows that the use of the tunnel spoil in shotcrete used in the access tunnel in Wolf spare a considerable amount of mineral resources and also reduces the environmental pollution, on several indicators”, Tobias Cordes explains.

Low-level CO2 concrete and shotcrete

In investigations at the University of Innsbruck optimized concrete recipes were developed which have low CO2 emissions and fulfil the requirements on site. Life cycle assessments (LCA’s) were realised and confirm the greening effects of the different low- level CO2 concretes.

“Further studies enable the use of low-level CO2 shotcrete in the near future which delivers also a considerable boost to a lower material’s sintering potential and an increase of the resistance against sulphate attack. Both have a major impact on future maintenance of the overall infrastructure”, says Tobias Cordes.

stefano.jpgGeothermal energy exploitation

The environmental potential of the exploitation of geothermal energy from tunnels is very high for both open loop (drainage water) and closed loop (energy lining) configurations.

“It can provide free heating (and cooling when necessary) to end-users in the areas affected by underground infrastructures and, if correctly promoted, it can even reveal to be an innovative instrument to increase acceptance of construction works by local communities”, Stefano Casale explains.

The economic value of the geothermal energy exploitation can be high, if the estimations of effective underground temperatures and thermal parameters are accurate. Estimation errors can underestimate the investment costs or overestimate the exploitable energy and fluid working temperatures.

Regarding the two possible configurations, the thermal use of drainage water can appear more convenient with respect to the energy lining, because there is basically no need of modifications To tunnel projects; nonetheless, the use of drainage water should respect environmental restrictions, which change accordingly to the area and administrations involved, while energy lining has practically no interaction with the environmental rules.

Moreover, in both cases designers have to face the same challenges in linking energy extraction to energy users, which in mountain territories are generally widespread. N

ew advancements in district heating systems (such as the use of “cold” district heating) will be necessary to fill this gap.

“Economic value and marketability of energy lining will depend on the effectiveness of inserting the heat exchangers inside the tunnel; the perfect balance must be found among the value of the investment, the timing for installation, the integration within the construction procedures, the safety for workers and the reliability of fittings and connections”, says Stefano Casale.

High potential for transferability of results to European stakeholders

The potential transferability, according to the corridor scope, of the most measures is very high.

“But the sustainability of each measure is project dependent and has to be evaluated by own life cycle assessments,” says Tobias Cordes.

The work with will continue

Even if the Swiftly Green project has come to an end, the BBT studies will continue.

“At BBT the work on a sustainable tunnel is ongoing. Theexisting and also new greening innovations are developed further in several master studies in cooperation with the universities and experts,” says Tobias Cordes