Detailed engineering geological investigations and numerical modelling for a planned road tunnel in Bhutan Himalaya
The Himalayas is generally characterized by steep slopes, lofty hills, and complex geological and tectonic settings. Hence, detailed engineering geological investigations are warranted for planning new underground projects in the Himalayas. This paper describes a feasibility study performed for a planned road tunnel in Bhutan. The study included engineering geological mapping, rock mass characterization, geophysical investigations and numerical modelling for verifying the rock support requirements in the planned tunnel. The numerical simulation results indicated that the recommended support, based on the Q-system, should be efficient to prevent instabilities for poor to good rock qualities. However, for very poor and extremely poor rock qualities, where the Q-values are below 1 i.e. (Q<1) rock support may need to be reinforced when the overburden exceeds approximately 1000 m.