SELI TBM Breaks Through Dai Ninh Headrace Tunnel in VietnamAfter 20 months of work on the headrace tunnel of the Dai Ninh hydropower project, Cavico Corporation announced that the tunnel has broken through on 14th July, 2006. The headrace tunnel is nearly 13 km in length, of which 5,911 metres were excavated using the drill-and-blast method as per New Austrian Tunnelling Method (NATM), i.e. in top heading / bench sequence, and 7,057 metres were constructed using a TBM. The blasted section started on 14th December, 2003 and finished two months ahead of schedule by 18th November, 2005. A two-boom drill rig H282 was supplied by Atlas Copco. The explosives were Orica P3151 supplied by Orica. The TBM started on 30th November, 2004. Visit www.atlascopco.com and www.orica.comThe Dai Ninh hydropower project is being constructed by the joint venture of main contractors Kajima-Kumagai-Song Da. Cavico is working as a subcontractor on the project and is responsible for the headrace tunnel and the surge tank construction. Cavico has provided approximately 300 engineers and technicians to the Kajima-Kumagai-Song Da JV to operate and oversee the TBM. Visit www.cavicocorp.com/tunnel_dn.html The 5.48 m-diameter double shield TBM is a SELI machine, type DSU model 054806, designed, assembled and tested in SELI's workshops in Aprilia by the technological department. SELI supplied the TBM and has collaborated throughout the construction of the tunnel by also supplying spares and technical assistance and by designing the prefabbricated lining. SELI sold the TBM and associated technical and design services to the Kajima-Kumagai-Song Da JV. Since 1992, SELI builds TBMs for its own use or for special projects at the request of clients, as is the case for the Dai Ninh scheme. The cutterhead is equipped with 432 mm cutters and provides a maximum thrust of 9,612 kN. It rotates at a speed of 0-11 rpm. The cutterhead drive power is 1,575 kW (5 x 315 kW). The Dai Ninh hydropower project is the first project in Vietnam to utilize a TBM. The tunnel lining consists of 30 cm-thick precast concrete segments. The finished internal diameter is 5.16 m. The geology consisted of sandstone, andesites, dacite and rhyolite. Visit www.selitunnel.comThe 300 MW Dai Ninh hydropower plant represents an investment of nearly VND7 billion through a bank loan from the Japan Bank of International Cooperation (JBIC) to ensure the stable supply of electric power in southern Vietnam. 36/06.