Evaluation of Slope Stability in Pelosika Dam Spillway Tunnel Using Limit Equilibrium and Finite Element Method

This paper uses the Limit Equilibrium Method (LEM) and Finite Element Method (FEM) to determine the safety factor for the slopes of the Pelosika dam tunnel portal. LEM uses the Bishop and Spencer method. Slope stability analysis was carried out on residual soil and schist geotechnical unit conditions. Soil failure criteria using Mohr-Coulomb and Generalized Hoek-Brown failure criteria in rock parameters. The stability analysis parameters include cohesion (c), internal friction angle (ϕ), unit weight (γ), Uniaxial Compressive Strength (UCS), Geological Strength Index (GSI), constant mi, disturbance factor (D), material constants (mb, s, a). The difference between LEM and FEM safety factor obtained are lower than 5%. Based on the minimum safety factor criteria (SNI 8460, 2017) are the inlet slope and outlet slope have an unstable condition. Analysis with FEM can determine the displacement and maximum shear strain on the inlet and outlet slopes of 0.08 m, 0.02 and 0.02 m, 0.01, respectively.