Risk analysis of TBM tunneling projects based on generic bow-tie risk analysis approach in difficult ground conditions

Abstract

Usage of tunnel boring machines has become the most popular underground excavation method to meet recent underground infrastructure development demands because of the high advance rate associated with this approach. However, using a tunnel boring machine for tunnel construction under difficult ground conditions carries the potential risk of causing undesired events. Determining the exact geological ground conditions before commencement of the project is almost impossible, rendering this industry to be fraught with high risk. Bow-tie risk analysis has emerged as a powerful tool for studying the risk management of undesired events in several high-risk industries but is yet to be comprehensively studied in the context of underground rock engineering. This paper presents a novel risk analysis methodology based on a generic bow-tie method for systematic assessment and management of risks associated with tunnel boring machine in difficult ground conditions. The bow-tie method integrates the fault tree and event tree analyses methods that follow a cause-consequence methodological approach centred on the common undesired event. The proposed risk analysis technique serves as a powerful tool that can aid tunnel boring machine professionals in systematically investigating, evaluating, and mitigating the inherited risks associated with tunnel boring machine in difficult ground conditions. For validation, the proposed methodology is applied to the twin tunnel boring machine project conducted in the Himalayas, and the results demonstrate its applicability as an effective risk analysis method.