Evaluasi Massa Batuan Terowongan Eksplorasi Uranium Eko-Remaja, Kalan, Kalimantan Barat

Eko-Remaja uranium exploration tunnel, Kalan, West Kalimantan is one of the important facilities for uranium deposit research. The tunnel was built in 1980 with a length of 618 meters penetrating Eko Hill on both sides. The rock inside the tunnel is relatively compact, but it has weak zones in some area. Ground supporting is a method used to overcome the soil and rock collapses which occurred in the tunnel weak zones. Installation of ground supporting system throughout the recent time based on the soil collapse pattern, which occurred when the tunnel opened without any specific study related to rock mass characterization and the requirement of ground support system. This research conducted to evaluate the safety level of Eko-Remaja tunnel and the suitability of ground support location. The evaluation performed by comparing the rock mass characteristics using Rock Mass Rating (RMR) method between the installed rock support and uninstalled rock support locations. Based on the analysis result, RMR value on the installed ground support is classified as class IV or poor rock. Meanwhile, on uninstalled location, the rock is classified as class II or fair rock. Based on the correlation between RMR calculation result and Eko-Remaja tunnel roof span, it is concluded that tunnel ground supports position which are represented by observation location on 38 m, 73 m, and 165 m depth are suitable with rock mass characterization system using RMR method.