Upgrading of Ageing CERN Underground Infrastructure to Fulfil the Space Requirements of New Facilities at CERN

Particle accelerator technology is constantly being developed, and new equipment and machines replace the former ones to keep pushing the energy and intensity frontiers. Therefore, in order to meet the space requirements of new equipment, the infrastructure often needs to be modified, and given its rigid nature, this presents a challenge for the civil engineers to provide the needed space without compromising the safety and serviceability of the structures. In this paper two underground works are presented: a new cross-passage tunnel for the AWAKE experiment completed in 2014 and the future SPS Beam Dump. The challenges that must be faced are: (a) to make sure that the movements of the adjacent structures remain within admissible limits, (b) to design and execute the works such that the life span of the structure is not reduced, (c) To ensure the effectiveness of existing and new drainage systems during and after the works. For these purposes, in the frame of future tunnel asset management, the use of novel and conventional monitoring techniques plays a crucial role as it can predict in real time potential tunnel deformations which can lead, in the worst scenario, to tunnel failure