| Summary: | This paper presents the characterization of igneous rock masses for the design of tunnel excavation methods and support systems. The subject of this research is the Bintang Bano Irrigation Tunnel located in Sumbawa Barat, Nusa Tenggara Barat. This tunnel was built as a container to channel water potential from the Bintang Bano Dam to the surrounding area. The purpose of this study was to determine the tunnel excavation method and support system during tunnel design and construction and estimate standing time based on rock mass classification. This research was conducted using primary data and secondary data collection was carried out to achieve the research objectives. The results showed that there was only one type of rock unit along the tunnel, namely andesite rock unit. The andesite rock along the tunnel has a uniaxial compressive strength (UCS) with various values, which is between 4.24 – 93.23 MPa with very weak to strong rock classification. Based on the RMR value, the andesite rock in the tunnel appears to be divided into two categories, namely poor rock and fair rock. Suggested excavation techniques and tunnel support systems along the tunnels vary based on rock mass categories calculated using the RMR method.
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