Stability Analysis and Strengthening on Zona Karst of Seropan Cave Walls

Abstract

The Indonesian state has many caves in several regions with unique legends and high cultural values, including Sang Hyang Sirah Cave in West Java, Seropan Cave and Semar Cave in Central Java, Liangkabori Cave on Muna Island and others. Seropan Cave has a large potential of water resources, especially in the karst area in the form of water flows in underground rivers. This study aims to analyze strain stress that occurs due to karst conditions on variations in groundwater level. Analysis method used finite element and plan strain model with the help of Plaxis v8.6 Software. The analytical approach is performed on the appearance of the cave with normal water level conditions, flood water levels and extreme use of shotcrete reinforcement, rock bolt and a combination of both. Material properties at the location are taken from the results of research and testing of the Seropan Cave IWRM laboratory and UGM Technical Team. The simulation results show that the existing conditions require wall reinforcement. Wall reinforcement uses 7 cm thick shotcrete and rock bolt with a diameter of 2 cm 4 m long with the distance between rock bolt is 2 m. Strengthening combination of rock bolt and shotcrete gives the highest safety factor of 2.01 while in earthquake conditions, it reaches 1.76. Combination wall reinforcement is quite stable against static and dynamic loads.