By lyndamyer
Due to completion of over than half of tunneling process on the Nepal Sunkoshi Marin Diversion Tunnel Project, construction is five months ahead of schedule, and more than 6.666km of the tunnel has been completed by China Railway No. 2 Group Co Ltd and China Overseas Engineering Group Co Ltd.
As the first TBM tunnel to pass through the Kathmandu spiral geological structure, the Nepal Sunkoshi Marin Diversion Tunnel is also the only high-buried, large-diameter single-head TBM tunnel under construction in Nepal.
The geological condition of the path of this 13.3km-long tunnel comprises of high water inflow, extrusion rock, geothermal, rock burst and a fault zone.
October 2022 was the commissioning date of this 6.4m diameter Robbins TBM, which’s average advance was 833.3m per month and in May it achieved a maximum of 1,136m.
Rationally adjusting cutters, installing over-excavation cutters, increasing the grouting volume, refining organizational processes, maintaining equipment maintenance, as well as supporting the supply of materials and equipment, were the methods that used by TBM team to overcome the challenging geology. The TBM also features a tapered design to reduce the risk of its becoming stuck in squeezing ground.
In order to improving electricity supply in the area, the diversion tunnel is linked to a new 28.6MW surface powerhouse on the Marin River. It is slated to 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.
