Manufacturing of the first tunnel boring machine (TBM) to be used in Nepal has just been completed and the first parts are now on the way to the construction site in the southern Himalayan Mountains.
The 5.06m diameter double shield TBM was built by Robbins for construction of the tunnels associated with the irrigation and hydroelectric Bheri Babai project by contractor China Railway No.2 Engineering Company.
The TBM will drive the headrace tunnels through a mix of sandstone, mudstone and conglomerate and will have to withstand squeezing ground, high levels of water ingress and fault zones with maximum cover of up to 820m.
The Nepalese government chose the TBM solution over the traditional drill and blast method because of the faster mobilisation and advancement rates offered by a mechanised approach. The Ministry of Irrigation has said that drill and blast excavation would have taken 12 years for the project’s 12.2km long tunnel to be completed.
The TBM is expected to be launched in November this year.