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DIVERSION TUNNEL WALLS STABILITY ANALYSIS USING FINITE ELEMENT METHOD AT TIGA DIHAJI DAM CONSTRUCTION, SOUTH OGAN KOMERING ULU, SOUTH SUMATERA PROVINCE a) Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta, Indonesia Abstract The diversion tunnel is one type of tunnel in the Tiga Dihaji dam construction that used for diverting the river flow along the main dam construction. The diversion tunnel uses a tunnel construction design with a diameter of 7 meters and a tunnel length of 595 meters consisting of several construction elements including the tunnel walls along the trace. It is necessary to study the stability of the tunnel walls to ensure that the walls are sufficiently stable after the construction is finished and all the supports system are already installed. Analysis of the stability of the tunnel walls is carried out using the Finite Element Method (FEM) with a 2D model to obtain the Safety Factor (SF) and total displacement value. To support the tunnel walls stability analysis, it is necessary to conduct laboratory tests to determine several parameters including the Uniaxial Compression Strength (UCS) value, cohesion value and inner shear angle value. In addition to laboratory tests, rock mass classification using the Geological Strength Index (GSI) method were conducted and the properties of the supports system was defined as one of the main inputs to obtain the Safety Factor and total displacement value. As the result, the tunnel walls Safety Factor value is more than 2 and the total displacement value is below 10 cm. Both results of the walls stability analysis show that the diversion tunnel is on a stable condition after the construction and there is no need to add or modify the support system that already installed. Keywords: Diversion Tunnel, Walls Stability, Finite Element Method, Safety Factor, Total Displacement Topic: Interdisciplinary Earth Science and Technology |
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