Geodetic network design and strategies followed for drilling a 25 km tunnel for high speed railway in Spain

SUMMARY During the last years several large high-speed railway tunnels have been built in Spain. To solve these projects, technical and scientific problems have been solved from the geodetic and surveying point of view. These studies have allowed us to set a methodology that optimizes the performance of this kind of works in the world of Civil Engineering. We have applied our studies to the Tunnels of Pajares that are the second longest ones in Spain with a total longitude of about 25 km. The studies summarize the design of the geodetic networks to support the guidance of the TBMs used as well as the election of the observations to be done, the instrumental to be used and the observation and computation procedures to be followed. A special emphasis has been taken into account for the treatment of the uncertainty of the coordinates, displacements and breakthrough obtained during the drilling tasks. The article shows the results obtained and the conclusions that can be followed in order to successfully complete a similar project.