Italian contractor CMC di Ravenna broke through on the 13.3km long Lot V Yellow River Diversion tunnel project in China on 27 September after just 10 months, six months ahead of schedule Impressive production rates exceeded 1,600m in both March and August (T&TI, Feb 2001).
After award of the $31M Lot V contract in April 2000 by the client, the Shanxi Wanjiazhai Yellow River Diversion Project Corporation (YRDP), CMC began tunnelling at the end of November 2000 using a Robbins 4.8m diameter double shield hard rock TBM. The TBM, equipped with 34x432mm back loading cutter discs, dealt easily with the limestone, dolomitic marls and clayey dolomites. But in June the TBM encountered a major setback at chainage 8740m when, due to a mechanical fault, the machine stopped in a squeezing area of over consolidated marls that lead to a shield blockage. Hand excavation around the shield freed the machine in only 10 days before boring resumed.
The contractor lined the tunnel with TBM erected 1.2m wide steel reinforced concrete hexagonal segments, four per ring, to leave a 4.2m i.d. with two rings being installed per advance. Back filling of the annular gap was carried out with pea gravel immediately after segment erection followed by cement slurry injection.
The Robbins will now be dismantled and returned to the client for future use on the North Line of the YRDP.
The $1.3bn YRDP, a 140km long aqueduct mostly underground, will convey waters of the Yellow River from the border with Inner Mongolia, south to the Shanxi Province capital Taiyuan, alleviating the area’s chronic water shortage. The scheme is financed by the World Bank, the Shanxi Province and the Italian government.
