Tunneling Challenges in Himalayan Region—A Review

Himalayan mountain is one of the most unstable regions due to adverse geological and climatic conditions. Since the Himalayas are a young mountain range with varied geological features, numerous problems like difficult topography, thrust and shear zones, sequences of rock fold and bedding plane, in-situ stresses, overburden of rock, seepage due to the rainfall, geothermal gradient, gas infiltration, seismic effect, etc., make it difficult to conduct tunneling activities in the Himalayan region. These challenges result in significant increase in cost and duration of the project. Even though contemporary tunnel construction technologies are presently being utilized in many urban tunneling projects in India, their utilization for mountain tunneling is still infrequent due to issues in their deployment. When the right solutions are conceived and put into effect in tunneling in Himalayas, it may decrease time and cost overruns with simultaneous enhancement in the safety and stability of the construction and tunnel infrastructure, respectively. Hence, a systematic review is conducted in this paper to consolidate the findings of the reported studies on challenges and possible solutions and action plans for tunnel construction in the Himalayan mountainous regions in India.