Nepal diversion tunnel makes good progress
1 August 2023More than half of tunnelling has been completed on the Nepal Sunkoshi Marin Diversion Tunnel Project, and construction is five months ahead of schedule.
China Railway No. 2 Group Co Ltd and China Overseas Engineering Group Co Ltd have completed more than 6.666km of the tunnel.
The Nepal Sunkoshi Marin Diversion Tunnel is the first TBM tunnel to pass through the Kathmandu spiral geological structure. It is also the only high-buried, large-diameter single-head TBM tunnel under construction in Nepal.
The 13.3km-long tunnel passes through difficult geological areas such as high water inflow, extrusion rock, geothermal, rock burst and a fault zone.
Since the 6.4m diameter Robbins TBM was launched in October it has set an average monthly advance of 833.3m and in May it achieved a maximum of 1,136m.
The TBM team has overcome the challenging geology by rationally adjusting cutters, installing over-excavation cutters, increasing the grouting volume, refining organisational processes, maintaining equipment maintenance, and supporting the supply of materials and equipment. The TBM also features a tapered design to reduce the risk of its becoming stuck in squeezing ground.
The diversion tunnel is connected to a new 28.6MW surface powerhouse on the Marin River to improve electricity supply in the area. It will provide farmland irrigation in the districts of Dhanusha, Mahottari, Sarlahi, Rauthat and Bara in the Terai Plain, diverting water from the Sunkoshi River to the Marin River.
