By Ashley Karen
China Railway No.2 Group and China Overseas Engineering Group, the Chinese contractors, are five months ahead of schedule in building a complicated 13.3km tunnel in Nepal.
The contractors have finished 50% of the tunneling mileage on the Nepal Sunkoshi Marin Diversion tunnel until now.
The project includes a TBM (tunnel boring machine) passing through the ‘Kathmandu spiral’ geological structure for the first time.
The tunnel is envisioned to link to a new 28.6 MW surface powerhouse on the Marin River to help a power supply shortage in the area. In addition, it will assist with irrigating farmland in several surrounding districts by redirecting water from the Sunkoshi River to the Marin River.
China Railway Group claimed the tunnel passes via “unfavorable” geological areas with high water inflow zones, fault zones, and squeezing ground. All of this involved “great difficulty” and “increased construction risk”.
For alleviating some of those risks, geological engineers have been studying and reviewing the geology along the tunnel, carrying out deep drilling and supplementary surveys in the fault zone area to comprehend the site’s geological conditions.
The scheme began on 14 October 2022, once the contractors launched a 6.4m diameter Robbins double shield tunnel boring machine. It has worked an average of 833.3m of drilling monthly and a maximum monthly distance of 1136m.
