Implications of Blasting-Induced Vibration on the Stability of Hydroelectric Power Tunnel

Abstract

Abstract An adit tunnel is a horizontal opening used for accessing a headrace in a hydroelectric power tunnel. PT. Kerinci Merangin Hidro is actively engaged in the construction of hydropower plants, with a focus on creating two types of tunnels. During blasting activities with a target progress rate of 50 m in a month, high explosives are commonly used between 500 and 600 PCS days. However, this method leads to vibrations that negatively impact tunnel stability, causing the formation of new cracks in walls. Data processing was conducted using Blastware 10.7 instant software, RS2/Phase2 software and the finite element method. The classification of rock masses included the use of the Rock Mass Rating (RMR) and the Q-System. The research results showed that Fair Rock class (III) rocks were identified at the six observation stations based on the classification of rock masses according to RMR 1989. There was a significant decrease in the weight of the rock mass before and after blasting at each station. The safety factor ranged from 1.26 to 6.00. A greater blasting agent weight per delay resulted in increased vibration across the six patterns. The most significant decrease in safety factors occurred only in pattern 6, with the highest tremor recorded at 1.1220 m/s2. Comparing patterns 5 and 6 with the same blasting agent weight per delay of 8.8 kg and equal explosive load of 550 kg showed that the highest decrease in safety factor values occurred in pattern 6. This phenomenon can be attributed to the fact that a shorter delay produces greater vibration than a longer delay time.