TBM operations are under way for the Xe-Pian Xe-Namnoy Hydropower Project in Laos. The 5.74m diameter Double Shield hard rock machine, manufactured in China by Australian manufacturer Terratec, will complete 11.8km of the 13.7km upper headrace tunnel for tunnelling specialist Seli Overseas, working under sub contract to South Korean turnkey contractor SK Engineering & Construction.
To witness the important milestone, a colourful ceremony was arranged and attended by officials from the client, Xe-Pian Xe-Namnoy Power Company, SK Engineering & Construction, Seli Overseas and Terratec.
After successful factory testing in December (2014), the machine was dismantled, transported to the remote site, and reassembled within approximately three months.
Following completion of site testing the TBM will now be advanced through 500m of tunnel adit excavated earlier by drill+blast. Once the TBM reaches the tunnel face, it will commence excavation and installation of the fully segmentally lined tunnel.
Geology consists primarily of two formations: the Tholam Formation consisting of mudstones and siltstones, and the Champa Formation including siltstones, sandstones and conglomerates. While available geological and tectonic maps show no major weak zones, faults are anticipated with the possibility of some water ingress. Seli Overseas reports that the tunnel is expected to cross several fault zones, some of which will be more than 20m wide.