Review of Underground Space Utilization and its Relevance in Nepal

Underground space, both open-cut and fully underground method, has been in use throughout the world for mining, storage, waterway, transport, and others from past centuries. But still the clear demarcation of ownership in terms of surface and underground is not clear in most parts of the world. The concept of underground space utilization is an evolving concept. The developed nations have opted for this option to accommodate growing urbanization need. Two modes of space utilization are reviewed for this paper, open excavation and full underground excavation. Also world case scenario is presented and is compared to the situation in Nepal. Social factors and geological factors in the context of Nepal are also addressed that have been crucial in case of some completed projects. Ambiguous underground rights in relation to surface ownership in Nepal is taken in account and example of some cities like Singapore, Tokyo, Helsinki is presented to make it clear how right segregation is possible and is needed for better underground space utilization. Historical evolution of Tunneling in Nepal is discussed along with the future designed and scheduled projects. Despite the geological complexity and lack of experienced manpower in the context of Himalayan geology the importance of underground space is highlighted because emerging researches and technological innovation around the world and also in Nepal have been confirming this concept now and again. As a conclusion for betterment and well managed cities in Nepal underground space would be an undefeated option in the long run.

Engineering Geological Design of Underground Works for Upper Madi Hydroelectric Project

Himalayan geology is termed as one of the youngest tectonic formations in the world. Tunneling in this region is hence complex in nature. The very complex geology in the region offers challenges in stability of even the best located underground structures. Tunneling in weak rock is more challenging in terms of stability and application of support. Moreover, in many occasion, prediction of the rock mass has been done optimistically in most of the underground projects in Nepal. In this paper, predicted versus actual rock mass condition has been compared for two already completed projects. Based on this needed support is calculated by empirical method for the project under investigation and later on verified by numerical analysis using the software Phase2. Stability analysis is also done for both high pressure headrace tunnel and underground surge shaft. Numerical method of analysis has an added advantage over empirical and analytical methods, particularly in complex geometry. The Phase2 code and the Hoek-Brown Failure criterion have been used to determine the state of stress, strength factor and deformations around the periphery and in the tunnel walls.DOI: http://dx.doi.org/10.3126/hn.v9i0.7069 Hydro Nepal Vol.9 July 2011 27-34

Developments in the geological exploration of Nepal

Prior to 1950, only sporadic geological observations by a few visitors were made in Nepal. With the opening of the country to foreigners in 1950, Nepal soon came into the focus of interest in Himalayan geology. It was the time of the classical "descriptive geology" with mapping as the primary objective. Several excellent monographs and the first geological maps of different parts of the Nepal Himalaya were produced. The best results were obtained in the richly fossiliferous "Tibetan" sedimentary zone in the north, whereas descriptions of the Central Crystalline zone and of the thick, unfossiliferous metasediments of the Lesser Himalaya reflected mainly the widely differing interpretations and conflicting views of the investigators; nappe structure vs. block tectonics was the main issue. .. With the advent of plate tectonics in the late 1960s, the Himalaya became the "collided range". Microstructural, mineralogical and geochemical studies in the search for stress and heat effects of subduction and collision on structure, metamorphism and magmatism became dominant and in Nepal concentrated on the Main Central Thrust, which was treated in terms of post­ collisional continental subduction. With it went a shift of emphasis from field to laboratory work, from observation to interpretation, from mapping to modelling, from fact to theory. The last thirty years were characterised by the strengthening and diversification of geological institutions in Nepal with the creation of a National Seismological Centre, the beginning of petroleum exploration in the southern foreland of the Himalaya, an intensification and modernisation of classical geological surveying and a strong engagement in the application of geology for engineering and natural hazard assessment purposes.

Underground Space for Infrastructure Development and Engineering Geological Challenges in Tunneling in the Himalayas

Being topographically steep and consisting of many rivers originating from the glaciers of the Himalaya, Nepal is gifted in water resources. As a developing country, Nepal needs to accelerate to develop its crucial infrastructures for the economic prosperity of the nation. This is achievable by developing the enormous hydropower potential available, making short and efficient roads through the steep mountain topography, extracting mines for various purposes, and providing cost effective solutions for the storage facilities. These developments are not possible unless tunnels and underground caverns are used. Due to tectonic activity, however, the rock mass in Nepal and across the Himalayan region is somewhat different in their engineering behaviour. These differences in mechanical behaviour are mainly caused by a high degree of folding, faulting, shearing, fracturing and deep weathering. As a result, severe instability problems associated with this complex geological setup have to be faced during tunnelling. This is the major challenge to be addressed in a scientific manner in order to make tunnel option more cost effective, feasible and safer. This paper delineates the possible areas where tunnels and underground caverns are needed and may play an important role in the socio-economic development of the nation, discusses the major geological challenges faced while tunnelling, and briefly describes methodologies to be used for analysing geological uncertainties. Key words: Himalayan geology, tunnelling, Nepal Hydro Nepal: Journal of Water, Energy and Environment Vol. I, Issue No. 1 (2007) pp. 43-49