Investigation of geological conditions beyond the excavation face using a MSP boring data monitoring system

Abstract

Pre-investigation of geological conditions beyond the excavation face is crucial for assessment of safety and design in underground construction. This study developed a boring data monitoring system equipped for a multisetting smart-investigation of the ground and pre-large hole boring (MSP) machine that typically drills a horizontal distance of 50 m to reduce blast-induced vibration. The monitoring system was applied to the tunnel construction site, which drills 40 m with the MSP method to investigate the geological conditions ahead of the excavation face. In addition, the analysis results of the boring data were compared with the observed images taken inside the holes, using a borehole alignment tracking and ground exploration system. The analysis of the boring data indicated rapid changes in pressure and boring speed with changes in geological conditions. Furthermore, the ground conditions ahead of the excavation face can be classified into three stages based on the boring pressure and speed variations. Therefore, these boring data can be the basis for predicting the geological conditions beyond the excavation face without additional effort and processes, and can help in ensuring the safety and efficiency of tunnel construction projects.