STABILITY ANALYSIS OF MINING TUNNEL USING ROCK MASS CLASSIFICATION RMR AND Q-SYSTEM IN PT ANTAM, PONGKOR MOUNTAIN, BOGOR REGENCY, WEST JAVA

• Main Author: Cahya Nusantara Herdianto, Tedi
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/70340
• Institution: Institut Teknologi Bandung

Gold and silver of PT Antam are mainly sourced from Pongkor mine area, West Java. An Underground mining method is used in PT Antam Pongkor mining area. For underground mining, geology, geotechnical and geomechanics are important things for mine design (tunnel) to consider the safety and stability factors. Research area is located between 6o 39' - 6o 42' S and 106o 38' - 106o 40' E in Kubang Cicau mining area. The research object is mainly located on tunnel drift KKRB 1 474 Utara, KK 536, KK 474 Konek, and KK 474 Utama. This research was conducted in order to determine the ratings of the rock mass using Rock Mass Rating (RMR) and Q-System classifications. The ratings from RMR and Q-System were used to determine rock support design recommendation for a tunnel. Evaluation of tunnel stability and numerical analysis based on collapse type were conducted afterward. Numerical analysis was conducted using finite element method by concerning the Strength Factor (SF) and support capacity. Based on field observation, lithology of KKRB 1, KK 536 and KK 474 Konek are composed of lapilli tuff, meanwhile KK 474 Utama are composed of lapilli tuff and tuff breccia. RMR classification show the rock mass class of III (fair rock) was located at KKRB 1 and KK 536 while the class of III (fair rock) – V (very poor rock) was located at KK 474 Konek and KK 474 Utama. Q-System classification showed poor rock mass class at KKRB 1 and KK 536 while the class of very poor rock – extremely poor rock was located at KK 474 Konek and KK 474 Utama. The rock mass parameters used in the RMR classification could determine that the location of KKRB 1 and KK 536 have showed wedge collapse type pattern, while the location of KK 474 Konek and KK 474 Utama have showed rockmass collapse type pattern. According to RMR classification results, rock support design recommendation of H-Beam, wire mesh, and rock bolts were proposed while the fiber reinforced shotcrete and rock bolt were proposed based on Q-System classification result. Numerical analysis and evaluation of rock support recommendation design from RMR classification resulted in a SF value more than 1.25 and the support capacity analysis has shown that the point of collapse has been able to sustain, while recommendation design based on Q-System classification showed there are still cases in a SF less than 1.25 and the support capacity analysis has shown that the point of collapse is in the critical area of collapse. Evaluation which is conducted from previous analysis showed that RMR classification is more suitable than QSystem classification to be applied at the research area.