Bolaños Tunnels

Name and location

Twin Tunnels named “Túneles de Bolaños”, located in the stretch Vilariño – Campobecerro of the High Speed Railway Line Madrid – Galicia.

Key features

Total length of stretch: 7900m

Tunnels length: 6750 m each tunnel (bored in sandstones, limestones and shales)

Total cut and cover tunnels length (at each end of main tunnels): 200m

Exterior diameter: 9.50 m

Segments depth: 370mm (universal ring with seven segments)

Ring length: 1.6m

Maximum cover over tunnels: 200m

Maximum water table height over tunnels: 140m

Materials: reinforced concrete.

Construction: Tunnels bored by TBM. Cut and cover tunnels are casted using rings as internal formwork and mobile exterior formwork.

Property

ADIF Administrador de Infraestructuras Ferroviarias

Construction

ACCIONA INFRAESTRUCTURAS + FCC CONSTRUCCIÓN SA + CONTRATAS Y VENTAS Y COLLOSA + CYES CONSTRUCCIÓN.

2013 – 2016

Intervention

Construction project for the Joint Venture. Technical assistance and engineering construction works focused on the design of cut and cover tunnels; geotechnical modelling of main tunnel and scape galleries; design of segments (geometry and reinforcement).

Description

Drawings

Construction pictures

General information

This stretch is located in the stretch Vilariño – Campobecerros of the High Speed Railway Line Madrid – Galicia, near Orense.

The major part of the stretch corresponds to a twin tunnel bored using TBM. These tunnels reach depths of 200m in sandstones, limestones and shales, with water pressures up to 140m, and go through several geological faults.

Five types of segments have been designed, which are capable to support axial loads ranging from 3500kN/m to 8500kN/m (axial load acting on segment due to earth and water pressure).

All segments have the same geometry:

Seven segments each ring (universal ring). A maximum curvature of 300m in plan or elevation can be reached if necessary.
Exterior diameter: 9500mm
Segment depth: 370mm

Concrete qualities for segments ranged from HA-40 to HA-60.

Due to the high water pressures acting on the tunnel, an innovative radial joint, with double sealing, has been designed. The use of a double sealing reduces considerably the available cross section in joints to support acting axial loads, so a highly engineered detail of these joints has been developed.

Cut and cover tunnels were designed so segments of the main tunnels could be used as internal formwork. The exterior formwork was a conventional one.

Cut and cover tunnels have maximum cover of around 17m, but all of them have a significant imbalance in backfill height in both sides.

In all cases, the lower slab of cut and cover tunnels has been used to assemble or disassemble the tunnel boring machine, which has been used to bore both tunnels.