Summary of the Development of New Technologies for Submarine Immersed Tunnel Foundation Reinforcement and Settlement Control

Based on the immersed tunnel foundation improvement modeling and analysis of data through investigations and researches on immersed tunnel diseases at home and abroad, this paper proposes that the adverse loads and poor geology are main causes inducing settlement and diseases. On top of the review on technical innovations in typical immersed tunnel foundation improvement abroad, the innovation and advancement of immersed tunnel foundation improvement of Hong Kong-Zhuhai-Macao Bridge Project is introduced with emphasis and these technical innovations mainly comprise the technology of double-layer bed with both rigidity and flexibility, the technology of SCP(Sand Compaction Piles) plus surcharge loading in ground improvement, the settlement computation method based on CPTU of rebounding and recompression and determination of settlement control criteria and others new development. Furthermore, through analysis the corresponding foundation improvement countermeasures are provided in this paper to meet such construction challenges faced in the immersed tunnel foundation improvement of Shenzhong Link and those challenges are super-wide width varied immersed tunnel element, soft soil ground of sand pit, weathered rock softening in water, sandy soil liquefaction, intense siltation. Finally, as the State key study and development program, it is pointed out that the technical study on diseases inducing mechanism and corresponding pro-active prevention and control of submarine immersed tunnel founded on poor ground conditions shall be carried out based on the full consideration of interactive actions between the structure and its foundation and the technical route and main study contents are further proposed for reference of relevant technical professionals.