| Abstrak/Abstract |
Construction of the Bagong Dam's diversion tunnel commenced in 2022. The tunnel, stretching 480 meters in length and measuring 4 meters in dimensions, is positioned directly beneath the dam. Due to the change in the trajectory of the inlet portal, a thorough analysis of the slope stability of the inlet portal is essential. This report presents a comprehensive slope stability analysis using the finite element method (FEM), both with and without earthquake loading. It also includes data for FEM analysis such as subsurface lithology, drill core analysis, observations of the geological strength index (GSI), and pertinent laboratory results. The study area encompasses two main lithologies: moderate weathered calcipulverite limestone and slighly weathered andesite breccia. GSI observations on core drill samples indicate that calcipulverite limestone is poor to fair quality (31-51), and andesite breccia with interbedded claystone is poor to good quality (51-89). The results of the FEM analysis showed that the Critical Strength Reduction Factor (SRF) of the slope decreased after adding earthquake loads. Under static and earthquake loads, the excavated slope at the tunnel inlet with a slope of 45° has a critical SRF value of 4.81 under static load, and 4.62 under seismic load. Based on the calculated SRF value, it can confidently affirm that the condition of the inlet portal slope is safe. |
