Novel Technique for the UX15 Cavern Vault Support System

The overall LHC project schedule requires the civil engineering work to begin before the final LEP shutdown. The new caverns for the ATLAS experiment will be built in and around the existing underground structures at point 1. In order to make the best possible use of the time available for the LHC civil engineering before the shutdown of LEP, a particular arrangement for the construction of the UX15 cavern vault has been developed. The basic concept of this arrangement consists of the excavation of the cavern top heading and the installation of the concrete vault immediately afterwards, prior to the subsequent bench excavation after LEP shutdown. A temporary support of the dead weight of the concrete roof will be achieved by the suspension of the roof by 38 no. pre-stressed ground anchors of 225 tons capacity each. This support system will work up to the construction of the cavern base slab and walls and the completion of the permanent concrete lining.