Case study in Hong Kong
Treatment of C.D.G. with slurry shield TBM
Hong-Kong MTR WIL 703 (MTR Corporation to Dragages, Maeda & Bachy Solétanche Joint Venture) and Hong-Kong MTR 820/821 (MTR Corporation to Dragages Bouygues Joint Venture).
Slurry TBMs have been chosen in decomposed granite alignments so as to ensure safe boring conditions, both in Hong-Kong and in Singapore. Despite the fact that, in both cases, the GIBR gives a very wide variety of grain-sizes distributions, it is of major importance for the contractor at bidding stage to come to a sensible evaluation of the quantities of spoils which will be recovered by the Separation Plant, especially the extra-fines portion - 63µm.
The aim of this presentation is to compare the figures extrapolated from the GIBR with the ones obtained on the sites, and to adjust the simulations tools used for the sizing of the different components of the Separation Plant by the STP supplier, especially the excess mud treatment section.
Presentation of the projects
MTR WIL 703
These two tunnels (boring Ø 6.35m, 770m + 490m long) are part of the West Island Line (Sheung Wan to Sai Ying Pun), situated in a very congested urban area. Contract was awarded by MTR Corporation to Dragages, Maeda & Bachy Solétanche Joint Venture. Its first ring was bored in September 2011, and the tunnel was completed in november 2012.
The geological profile was showing about 31% of the drive in CDG, 42% in mixed face, and 21% in rock, with a small section representing 6% in Alluvium.