4 th International Engineering Symposium - IES 2015 March 4-6, 2015, Kumamoto University, Japan 1 Numerical Studies of A Tunnel Excavation and Its Effect on Stress Distributions around the Tunnel in Underground Bangalore Metro Project Ishaan Rajankar 1 and Dr. T.G. Sitharam 2 1 Undergraduate engineering student, National Institute of Technology Karnataka, Surathkal, India, 575025, Email: ishaanrajankar@gmail.com 2 Professor, Department of Civil Engineering, Indian Institute of Science, Bangalore, India, 560012, E-mail: sitharam@civil.iisc.ernet.in ABSTRACT: ‘Namma Metro’ or Bangalore Metro is a metro system which runs in the city of Bangalore situated in Karnataka, in the busy central districts to provide a sustainable public transport. Due to the presence of Gneisses and Granites which is a part of the Peninsular Granitic complex geology, the Tunnel Boring Machine is finding difficulties in proceeding in the Bangalore Metro Project. After analyzing the bore log report, a two dimensional, linearly elastic model and Elasto – plastic model is created using a finite element method software package, ABAQUS/CAE and the results have been compared with the tangential and radial stress distribution obtained using the Kirsch’s Solution a nd Bray’s Solution. In order to validate the accuracy of results derived from ABAQUS, and to determine its coherence with existing work, example problems were considered with Elastic and Elasto-plastic analysis. Several cases have been reviewed and summarized. This paper also includes an analysis to check the effect of the redistribution of stresses by varying the Lateral Earth Pressure ratio and to compare the stress distribution around the tunnel at different stages of construction which includes Boring, Lining, Grouting and insertion of Dowels. Further, results are presented to understand the difference in stresses in the presence and absence of Dowels present around the tunnel excavation. Keywords: Underground Bangalore Metro Tunnel; ABAQUS/CAE; Elastic Model; Elasto-plastic Model; Lateral Earth Pressure Ratio; Stress Distribution at different Stages of Construction; Stresses in Dowels INTRODUCTION Tunnels are the vital elements for everyday life of people, especially those living in heavily crowded urban areas. Tunnels are built to move people or materials in a precise route where the movement without a tunnel is impossible or it is impractical or inadequate. The salient features of the Bangalore Metro are given as follows:-The total length of the Bangalore metro line is 42.3 kms, which is divided into two corridors. The first one runs along the east – west corridor extending up to 18.1 kms and the other running along the north-south corridor is 24.2 kms long. The total length of underground section is about 8.7 km. The focus of this study is confined to the underground section with a twin tunnel for a length of 4.8 kms along the east-west section. Tunnels are bored using slurry TBM with an inner diameter of 5.6 m which is reinforced with a concrete lining of thickness 280 mm. The depth of the tunnel from the ground level is approximately 15 to 18.3m below the surface of the ground, the twin tunnel centres are 15.04 m apart from each other. The Tunnel Boring Machine (TBM) is successfully used to carry out the excavation process for the completion of the underground work in Bangalore using Helen and Margarita, two drilling machines, with a capacity of 11m per day. An Overburden of 10-12m is present above the TBM which has a diameter of 6.44m.