- The company has developed an innovative solution by adapting a double-shield tunnel boring machine and enabling the use of a belt conveyor for the muck, generating savings of up to 219 tons of CO2.
- ACCIONA, in a consortium with Sacyr, was awarded this project to design and construct the Mularroya dam, as well as construction of the diversion dam and pipeline, which includes construction of more than 12.6 km of tunnel.
The ACCIONA and Sacyr consortium was awarded the contract to design and construct the Mularroya dam in Zaragoza. The project includes construction of the diversion dam and pipeline, which involves constructing more than 12.6 km of tunnel with an internal diameter of 2.9 metres.
To construct the tunnel, ACCIONA has adapted one of its double-shield tunnel boring machines (TBM) to the needs of the project, which requires a single-shield rock TBM due to the geological complexity of the route.
The Works Construction Support Department has created an innovative solution, adapting the machine and making it possible to use a belt conveyor for the muck. This enhances the feasibility of the project and delivers a highly significant environmental benefit thanks to the use of more efficient electric-powered machinery, generating emissions savings of up to 219 tons of CO2.
The adaptation of the TBM has meant manufacturing a new cutter head adapted to the diameter required by the project, as the original machine had a drilling diameter of 4,100 millimetres, which the project needs to be 3,556 millimetres. Furthermore, the pipes for the main shield on the TBM also need to be different, modifying one of them and manufacturing a second one, while the rear shield has also been newly manufactured.
Given the length and reduced internal diameter of the tunnel, ACCIONA and Sacyr have opted to use a belt conveyor to extract the muck, minimising the use of engines, which will also be electric. This will therefore reduce any polluting gas emissions generated by transport inside the tunnel during its construction to zero.