Nepal’s first tunnel boring machine, a 16.6-foot-diameter Robbins Double Shield, is living up to the nation’s high expectations. The TBM, supplied in summer 2017 for the Bheri Babai Diversion Multipurpose Project (BBDMP), recently bored over 3,280 feet in one month and has been averaging an impressive 2,630 feet per month. The project is owned by the Government of Nepal’s Department of Irrigation (DOI) and operated by contractor China Overseas Engineering Group Co. Ltd. Nepal Branch (COVEC Nepal).
The decision to use a TBM for the BBDMP project—designated by the government as one of Nepal’s 11 National Pride Projects—was a departure for a nation where drill and blast has long been the preferred tunneling method. Early studies done on the tunnel path predicted that drill and blast excavation of the 7.5 mile tunnel would take close to 12 years to complete. The tunnel is located in the Siwalik Range, part of the southern Himalayan Mountains, where geology consists of mainly sandstone, mudstone and conglomerate.