- Project – Arnotegi Tunnel, Southern Metropolitan Bypass, section 9A Peñascal-Bolintxu
- Location – Arnotegi Tunnel, Bilbao, Basque Country
- Installation dates – March – August 2021
- Owner – Bizkaia Interbiak
- Consultant/Engineer – UTE Hegoalde II
- Constructor – UTE ARNOTEGI
- Installation company - Aquaprotección
- Type of works – Tunnel under infiltrating water
- Product – RENOLIT ALKORPLAN Tunnel C 35034 - Thickness 2.5mm - Quantity 105,000 m2
Section 9A of the Southern Metropolitan Bypass (VSM in its Spanish initials), which the Arnotegi Tunnels belong to, will be the first major lineal work in Bizkaia to apply BIM methodology in the construction phase of the project’s management, a requirement that was included for the first time in Interbiak’s tender documents. Section 9A has two tubes, 1,920 and 1,950 meters long. The total volume of the excavation of the tunnel is 424,447 m3. 105,000 m2 of geomembrane was delivered for the waterproofing.
The tunnel is constructed using the New Austrian Tunnelling Method (NATM) which integrates the principles of the behavior of rock masses under load and the monitoring of the performance of underground construction. By providing optimized support based on conditions observed in the field, it uses a “design as you go” approach.
This method usually requires the installation of a waterproof sheet between the membrane and the cladding. The dome and the side walls had to be waterproofed, and at the same time the water had to be conducted to the drainage networks.
Due to the method chosen for the waterproofing of these tunnels, it required a waterproof sheet which would be resistant to both perforation, roots, aging and deformation, as well as being flexible with a large capacity to be elongated.
The most logical solution was the RENOLIT ALKORPLAN Tunnel C 35034 sheet, with a thickness of 2.5 mm. It is a homogeneous sheet which can be stretched to an elongation of 350%. This sheet brings with it many advantages: it extends the useful life of the structure and associated installations containing it, thus reducing the maintenance costs related to the water pump and deterioration of the concrete. Similarly, it prevents dripping on the carriageway platform.
The choice of the RENOLIT ALKORPLAN Tunnel C 35034 has also allowed the engineering designs to be simplified, given the existing independence between the support and the cladding, providing savings in terms of both time and money.
Thanks to its perfect watertightness, the Arnotegi tunnel project proposes a series of actions directed towards encouraging innovation in its strategic fields, such as the placement of remote sensors which are able to monitor the tunnel’s execution control and the behavior of the structures during the operating phase.
In order to protect the environment, an endotherapy technique is used for the effective eradication of invasive species, the use of sensors and tubes able to remotely measure the main environmental parameters, the use of drones to monitor the environmental control, the installation of hydrodynamic separators to minimize pollution coming from the runoff waters from the carriageways during the operating phase of a road. All this, together with the final massive cinematic data collection by means of a mobile scanner of the lineal works to be carried out once they are completed.