Empirical analyses of the excavating method and support system based on engineering geology of the Rukoh Dam Suppletion Tunnel, Pidie Regency, Aceh Province, Indonesia

Abstract

In the design of the Rukoh Dam Suppletion Tunnel, the rock mass quality had not yet been evaluated. Whereas the evaluation empirically affects the stability and support system of the tunnel. This research aimed to provide recommendations for excavation methods and support systems in tunnel construction based on the RMR and Q-System methodologies. The research investigation was conducted by surface geological mapping and assessing the rock mass quality from drill points. The results showed that the tunnel area consists of calcareous siltstone. Meanwhile, the tunnel axis consisted of poor-quality calcareous siltstone based on the RMR value. Following the Q-value, the quality of the calcareous siltstone ranges from very poor to extremely poor. Based on empirical analysis, the tunnel's excavation methods were the top heading and bench methods with 0.6 to 10.0 hours of stand-up time. The proposed support systems analyzed from RMR and Q-value were rock bolt, wire mesh, shotcrete, and steel sets. This analysis had implications for minimizing the risk of failure at the tunnel site due to poor rock mass quality. Even though an empirical method aids in the design, numerical studies are required to bolster the recommendations.