STABILITY ANALYSIS IN NANJUNG DIVERSION TUNNEL SUPPORTING SYSTEM USING TWO-DIMENSIONAL NUMERIC MODEL WITH FINITE ELEMENT METHOD

• Main Author: Wahyudin, Yuyun
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/40264
• Institution: Institut Teknologi Bandung

The Nanjung Diversion Tunnel is one example of a twin civil tunnel used to increase the water flow rate of the Citarum River in the Curug Jompong area. Most of the structure of this tunnel is built on sandstone lithology which has poor rock strength. The excavation process in the tunnel will affect the natural stress around the opening hole. In poor rock materials, a support system is needed to maintain the stability of the opening holes. Therefore, in this study a stability analysis of the Nanjung Diversion Tunnel support system will be conducted. The first step is to do a comparison between the actual support that has been used against the empirical support recommendations based on the classification of rock mass. Then an analysis was carried out on the results of the two-dimensional numerical modeling of the finite element using 3 stability criteria. The stability criteria used in this study are total displacement, strength factor, and safety factors. Tunnel stability analysis using the Mohr-Coulomb collapse criteria. Some assumptions are used such as isotropic material, hydrostatic stress, flat and symmetrical soil surface, etc. Modeling is made into 9 stages. Before installation of a support, the tunnel opening has experienced relaxation of 60%. To facilitate the analysis process, 6 review points are determined in each tunnel. In the modeling results, it is generally obtained a graph of total displacement that has a positive trend, strength factor and safety factors that have a negative trend. The maximum total displacement (deformation) obtained at the final stage is 2.67 cm or 0.28% strain, strength factor and safety factor ? 1 at all review points. With the results of the modeling it was concluded that the support system in the Nanjung Diversion Tunnel construction was stable.