Records tumble at the Cabrera Tunnel: Never before has a TBM tunnelled so fast

The S-373 Herrenknecht Double Shield tunnel boring machine with a diameter of Ø 9.69m reached its target on September 25, 2008. The machine completed the shell of the second tube of the Cabrera Tunnel in the northeast of Spain – 5 months ahead of schedule. Tunneling work for the two almost 6km long railway tunnels started on July 27, 2007. Thus, the planned overall construction time was cut by a quarter.

First record as early as November 2007
Construction work for the first tunnel tube started already three and a half months after the factory acceptance of the TBM in Schwanau on April 12, 2007. Top daily performances of up to 83.2 meters showed that the S-373 tunnel boring machine was optimally designed for the geology. In November 2007 alone, a total of 1,600 meters of tunnel were excavated. The tunnelling of the first tube was completed only six months after the beginning of the construction work. At that time, the Herrenknecht branch manger Juan Arroyo forecast the following for the completion of the second tube: "If everything continuous to runs smoothly, we can finish work in December 2008". His estimate was not completely accurate. Because tunnelling work was completed already at the end of September 2008. For the construction of the second tube, the site was logistically equipped in such a way that the tunnelling performances outmatched those achieved in the first tube. The lining segments were produced around the clock, and the production of the mortar to fill the space between the lining segments was extended correspondingly, so that the double amount of material was available all the time. After the beginning of the tunnelling work on the 2nd tube on May 5, 2008, the team achieved weekly performances of more than 400 meters on several occasions; on average, the machine excavated 284 meters of tunnel per week and laid 178 lining segments.

Double Shield TBM allows non-stop tunnelling
The Herrenknecht Double Shield TBM with a diameter of 9.69 meters drilled continuously through the rock. The TBM held fast to the rock using gripper plates, creating the necessary contact pressures for the tunnelling work. At the same time the lining segments were installed with the help of the lining segment erector. Concrete segments weighing up to 8.8 tonnes and one keystone create a ring with a width of 1.6 meters thus forming the frame of the tunnel.

The Spanish Herrenknecht branch managers Francisco Avila Aranda and Juan Arroyo mentioned several factors to explain the speedy progress in the tunnelling activities: the experienced construction site team of FCC Construcción S.A. and Construcciones Sanchez Dominguez-Sando S.A., the logistics system which was planned in detail and the tunnel boring machine which was precisely adapted to the geology consisting of hard limestone. Consultant and tunnelling expert, such as Dr. Ingeniero de Caminos, Canales y Puertos Don Felipe Mendaña are impressed at the speed achieved by the machine and the construction site team: "The right machine type was chosen for the geology: a double shield. This made it possible to carry out almost 100% of the tunnelling work in the "double shield mode", allowing the simultaneous installation of the tunnel lining and the excavation work. Furthermore, the construction site team, excellently trained and coordinated by the construction company and the perfect logistics system contributed to this extraordinary performance."

The La Cabrera Railway Tunnel
The La Cabrera Tunnel crosses beneath the Sierra de La Cabrera and overcomes a difference in height of around 170 meters with a gradient of up to almost 3 percent between the western and eastern portal. As part of the extension of the high speed railway network between Madrid and Valencia, the tunnel forms the core part of the 11.2 kilometer long section "Siete Aguas-Buñol". The plan is to put the tunnel into operation at the end of 2010, after the installation of the necessary railway technology.

Tunnelling performances in figures
1st tube
Beginning of the construction work: July 27, 2007
Completion: January 25, 2008
Tunnel length: 5,974.4m
Top daily performance: 83.2m / 52 lining segment rings (December 1, 2007)
Top weekly performance: 430.4m / 269 lining segment rings (week 47/2007)
Top monthly performance: 1,600m / 1,000 lining segment rings (November 2007)

2nd tube
Beginning of the construction work: May 5, 2008
Completion: September 25, 2008
Tunnel length: 5,966.4m
Top daily performance: 105.6 m / 66 lining segment rings (July 19, 2008)
Top weekly performance: 435 m / 290 lining segment weeks (wekk 30/2008)
Top monthly performance: 1,688m / 1,055 lining segment rings (July 2008)


Contact:
HERRENKNECHT AG.
Achim Kühn
Schlehenweg 2
77963 Schwanau
PH.: +49 (0) 7824-302-0
FAX: +49 (0) 7824-34-03
E-Mail: pr@herrenknecht.de
Internet: www.herrenknecht.de