Cavico Transportation has completed tunnel excavation at the 320MW Ban Ve hydropower project in Vietnam and work has started to place the in-stu concrete lining.
Last month, the contractor, a wholly owned subsidiary of Cavico Corp, holed through to complete the tunnel works. Most were undertaken by drill and blast except for a pilot raise bore on an inclined shaft.
A total of just over 1.5km was excavated, consisting of 1290m of headrace, 112m of inclined tunnel and 167m of adit.
The geology at the site consists of thick sandstone beds with slight fracturing in parts only, and a few small faults.
The 5.5m wide adit and the 6.5m wide horseshoe-shaped headrace tunnels were opened up by bench excavation, the faces drilled by a Jumbo H 282 two-boom rig with one split feed. To muck out the contractor used a Komatsu WA 350 side dump, and for transportation a Mitsui Emco T20 tunnel truck was employed. Shotcrete and rockbolts for excavation support were place by an Aliva H282 and the Jumbo, respectively.
For the inclined tunnel, the contractor used a 1.8m diameter Atlas Copco raise drilling robbin to open along the centre of the circular inclined tunnel.
Drilling in 2.2m steps, the pilot bore was expanded to the full 6.5m diameter by drill and blast benches of 2m depth, the spoil being dropped down the pilot bore for mucking out using a Cat 950 loader and Mitsui truck.
Cavico is using 6m long needle beam type formwork to place lining for the headrace. A steel pipe of 30mm wall thickness is to be placed in the short, inclined tunnel and fixed with reinforced concrete surround.
Client for the nearly US$395M Ban Ve project is Electricity of Viet Nam (EVN).
Cavico estimates that its portion of the scheme is worth approximately US$20M. The hydro project was designed by Power Engineering and Consultant Co, a member of the EVN group.
Elsewhere in the booming Vietnamese hydropower sector, Cavico helped to complete tunnelling works on the Bac Binh scheme last year.
Late stage excavation is underway at EVN’s 280MW Buon Kuop scheme, for which a JV including Cavico excavated a 8.2m-9m wide headrace, 7.7km long, and two 131m high by 21m diameter surge chambers.
The partners in the JV were: Cavico Bridge and Tunnel; Vimexco, a subsidiary of Vinaconex; and Vinavico, a separate venture between the parent groups.
