The Riam Kiwa Dam is situated in Banjar Regency, South Kalimantan, and its design incorporates a D-shaped tunnel. This study aims to investigate how groundwater levels affect the stability of the diversion tunnel at the Riam Kiwa Dam. This study will examine the percentage reduction in deformation caused by the tunnel reinforcing system. Surface geological observations, core drilling observations, and technical information on tunnels and groundwater levels from field observations, lab analyses, and BWS Kalimantan III Banjarmasin are all parts of the data that is needed. This analysis employs the finite element method (FEM) with Phase2 software from Rocscience, taking into account various groundwater level conditions above the tunnel. The research findings indicate that the groundwater table’s elevation influences the deformation experienced in the tunnel. As we approach the tunnel crest, the resulting deformation decreases. The reduction in groundwater levels will improve the tunnel’s stability. The implementation of reinforcement systems in tunnels substantially mitigates deformation values resulting from groundwater presence. We anticipate that the research findings will provide guidance to stakeholders on secure construction practices in the Riam Kiwa Dam diversion tunnel.
