ENGINEERING GEOLOGICAL AND GEOTECHNICAL CONSIDERATION IN NAGDHUNGA ROAD TUNNEL AND SUPPORT DESIGN

Abstract

In the field of civil engineering, tunnel design is considered to be one of most complex challenges engulfing various aspects. Road tunnels are an underground passageway, especially one for trains or cars that passes under a mountain, river, or a congested urban area. Nagdhunga Road Tunnel project is starting from Basnetchhap on eastern portal and passes under the Sisnekhola to Nagdhunga pass and reaches to the west side portal, and is 2450 m long. Compendiously, we can say that tunnel design deals with the geometric, hydraulic, support system and the structural analysis. Hence, in our project we have carried out the design of tunnels under the following headings; 1. Geometric design 2. Support system design In geometric design, we have determined the suitable shape of the tunnel, layout of tunnel, tunnel alignment. Support system design is all about the stability of the tunnel before, during and after the excavation. The appropriate rock support system was ascertained using rock mass classification system and tunnel was stabilized. Likewise 2D Finite Element Method (FEM) modelling was carried out using the software Phase2 version 7. The methodologies used for the design of the tunnel are: 1. Literature Review 2. Site Visits 3. Data Collection 4. Structural Analysis 5. Interpretation The designs were made and analyzed, resulting in various comparisons of different geometries, and providing the required data as expected from the designs