CHALLENGES ASSOCIATED WITH PLANNING AND CONSTRUCTION OF A ROAD TUNNEL THROUGH LESSER HIMALAYAN ROCK MASS – A CASE STUDY

19th WORLD CONFERENCE OF THE ASSOCIATED RESEARCH CENTRES FOR THE URBAN UNDERGROUND SPACE, Belgrade, Serbia, November 4-7, 2025. (Paper No: 2.12.114,  pp. 369-379)

 

АУТОР(И) / AUTHOR(S): Bimala Piya Shrestha, Krishna Kanta Panthi

 

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DOI:  10.46793/ACUUS2025.2.12.114

САЖЕТАК / ABSTRACT:

Tunneling is crucial in infrastructure development, including hydropower, irrigation, water supply, sewerage, and transportation sectors. However, these underground projects are often accompanied by uncertainty and risk, particularly concerning stability and safety. The Himalayan region, characterized by relatively young tectonics, varying geological conditions, and fractured rock mass, is prone to challenges associated with block falls and stress-induced instabilities. Several factors, including lithology, rock mass conditions, structural geology, in situ stress conditions, groundwater conditions, tectonic activities, and topography, influence the utilization of underground space. This study aims to understand and evaluate the behavior of the surrounding rock mass of a proposed road tunnel intended to connect the second-largest city, Pokhara, with the Kaligandaki Corridor. The proposed road tunnel traverses the Lesser Himalayan geological formation in central Nepal. The ground behavior has been characterized using Rock Mass Rating (RMR) and the Q-system of rock mass classification. In addition, stability conditions have been evaluated using both analytical and numerical approaches for various rock formations where varying rock mass quality and rock cover prevail. The majority of the tunnel stretch is characterized by poor-quality rock mass. The analysis identified wedge failure in the phyllite with intercalation of bands of metasandstone at the eastern portal. These conditions necessitate the implementation of stabilization measures consisting of systematic rock bolting and steel fiber shotcrete. Furthermore, some sections with highly schistose and fractured rock mass exhibited squeezing behavior, with the highest tunnel strain of 15.01%, indicating the need for specialized support measures to accommodate the anticipated ground deformation.

КЉУЧНЕ РЕЧИ / KEYWORDS:

Tunneling, Lessor Himalaya, Rock mass quality, Ground behavior, Stability, and safety

ПРОЈЕКАТ / ACKNOWLEDGEMENT:

The authors would like to acknowledge NORAD, which supported this research through NORHED II Project 70141 6: Capacity Building in Higher Education within Rock and Tunnel Engineering in Nepal, operated by the Norwegian University of Science and Technology (NTNU), Norway, in collaboration with Pashchimanchal Campus, Institute of Engineering (IoE-WRC), Tribhuvan University (TU), Nepal. The authors are thankful for both financial and moral support in conducting this research.

ЛИТЕРАТУРА / REFERENCES:

  • Aryal, M. (2025). The Kaligandaki corridor road gives new hope to isolated mountain communities. The Kathmandu Post (10-05-2025).
  • Basnet, C. B., Panthi, K. K, & Shrestha, P. K. (2014). Analysis of Squeezing Phenomenon in the Headrace Tunnel of Chameliya Project, Nepal. Hydro Nepal: Journal of Water, Energy and Environment, 13(13), 44–51. https://doi.org/10.3126/hn.v13i0.10039
  • (2013). Nepal Road Standard 2070. Department of Roads, 55.
  • Dwivedi, R. D., Singh, M., Viladkar, M. N., & Goel, R. K. (2013). Prediction of tunnel deformation in squeezing grounds. Engineering Geology, 161, 55–64. https://doi.org/10.1016/j.enggeo.2013.04.005
  • Evert, H. (2001). Practical_Rock_Engineering.pdf. Course Notes, 190.
  • http://ssrn.aviyaan.com/traffic_controller/get_detail/Pokhara, cited on September 4, 2025
  • (2018). Design and Construction of Road Tunnels : Part 1 Planning. 111.
  • (2019). Federal Democratic Republic of Nepal | Data Collection Survey on Urban Transport in Kathmandu Valley | Final Report. July 1–24. https://openjicareport.jica.go.jp/pdf/12326708_01.pdf
  • KC, D., Gautam, K., Dangi, H., Kadel, S., & Hu, L. (2022). Challenges in Tunneling in the Himalayas: A Survey of Several Prominent Excavation Projects in the Himalayan Mountain Range of South Asia. Geotechnics, 2(4), 802–824. https://doi.org/10.3390/geotechnics2040039
  • Norwegian Public Roads Administration. (2004). Road Tunnels 03.04.
  • Palmström, A. (1995). Characterizing Rock Burst and Squeezing by the Rock Mass Index. Design and Construction of Underground Structures, c(February), 23–25.
  • Panthi, K. (2006). Analysis of engineering geological uncertainties related to tunnelling in Himalayan rock mass conditions. In the Norwegian University of Science and Technology (Vol. 5, Issue February).
  • Panthi, K. K. (2012). Evaluation of rock bursting phenomena in a tunnel in the Himalayas. Bulletin of Engineering Geology and the Environment, 71(4), 761–769. https://doi.org/10.1007/s10064-012-0444-5
  • Panthi, K. K. (2023). Methods applied for the stability assessment in rock engineering. Journal of Nepal Geological Society, 65(September), 29–34. https://doi.org/10.3126/jngs.v65i01.57741
  • Panthi, K. K., & Nilsen, B. (2007). Uncertainty analysis of tunnel squeezing for two tunnel cases from the Nepal Himalaya. International Journal of Rock Mechanics and Mining Sciences, 44(1), 67–76. https://doi.org/10.1016/j.ijrmms.2006.04.013
  • Sapkota, N., & Paudel, L. P. (2018). Geological Study of the Lesser Himalaya in the Kusma-Baglung Area, Western Nepal. Bulletin of the Department of Geology, 20(1980), 29–36. https://doi.org/10.3126/bdg.v20i0.20721
  • Shrestha, P. K. (2014). Stability of tunnels subjected to plastic deformation – a contribution based on the cases from the Nepal Himalaya. 124.
  • Shrestha, P. K., & Panthi, K. K. (2014). Groundwater effect on faulted rock mass: An evaluation of Modi Khola pressure tunnel in the Nepal Himalaya. Rock Mechanics and Rock Engineering, 47(3), 1021–1035. https://doi.org/10.1007/s00603-013-0467-7
  • Su, Y., Su, Y., Zhao, M., & Vlachopoulos, N. (2021). Tunnel Stability Analysis in Weak Rocks Using the Convergence Confinement Method. Rock Mechanics and Rock Engineering, 54(2), 559–582. https://doi.org/10.1007/s00603-020-02304-y
  • Upreti, B. N. (1999). An overview of the stratigraphy and tectonics of the Nepal Himalaya. Journal of Asian Earth Sciences, 17(5–6), 577–606. https://doi.org/10.1016/S1367-9120(99)00047-4
  • Vlachopoulos, N., & Diederichs, M. S. (2009). Improved longitudinal displacement profiles for convergence confinement analysis of deep tunnels. Rock Mechanics and Rock Engineering, 42(2), 131–146. https://doi.org/10.1007/s00603-009-0176-4
  • Zhang, T., Zhao, J., Kuang, R., & Li, C. (2025). Stability Analysis and Support Optimization of Tunnel Surrounding Rock with Weak Interlayer Based on Catastrophe Theory. Buildings, 15(3). https://doi.org/10.3390/buildings15030507