The civil engineering works for the HL-LHC Project will be completed during Long Shutdown 3 with the construction of 28 vertical cores, each with a diameter of 1 meter and a height of 7 meters. These cores will enable the connection of newly installed powering and control equipment in the HL-LHC technical galleries to the new systems in the LHC tunnel.

The design and execution of these vertical cores were subject to significant technical constraints between 2018 and 2021, such as chamfered ends, Halfen channels for services, access, ventilation, water, dust, no diesel engines, etc. These constraints, combined with a two-phase schedule separating access to the HL-LHC and LHC works and a limited two-month construction window in the LHC, created considerable challenges to set up a good execution plan. Market feedback confirmed that the imposed timelines were incompatible with the technical and organizational constraints, necessitating a revision of the proposed construction schedule and project conditions to ensure feasibility.

Natacha Lopez presented the new strategy at the Chamonix workshop last week. Following an in-depth analysis of suitable techniques and on-site testing, a revised IT has been developed with more realistic conditions, particularly regarding scheduling. This revised IT, aiming to attract excellent contractors while promoting schedule optimization, provides companies with greater flexibility in selecting the construction methodology best suited to their equipment and workforce. Responses expected in March 2025 and adjudication in the Finance Committee of June 2025.