Multiphase Risk-Management Method and Its Application in Tunnel Engineering

For a better understanding of risk management and the optimization of risk mitigation, a multiphase risk-management method is proposed in which the assessment of risks is divided into two phases: the initial risk phase and the secondary risk phase. The initial risk phase is used for risk evaluation at the beginning of a project and can be quantified by the combination of probability and loss. If the initial risk is not acceptable, risk-mitigation measures are evaluated and the most appropriate measure will be adopted. The secondary risk phase involves identifying risks after implementing the selected mitigation measures for the initial risk, and the mitigation costs are also included. Obviously, the secondary risk must be lower than the initial risk. The task of a tunnel engineer is to select mitigation measures that result in the lowest secondary risk. During project execution, environmental factors may change, and deviations from the original design assumptions may take place. These phenomena have a knock-on effect on the risk profile, and a timely reevaluation of the risk scenario becomes necessary. Therefore, it is further proposed that the two-phase risk-evaluation process be extended to infinite phases. The novelty of the proposed method is characterized by its combination of a dynamic risk-management system and a timely reassessment of new risks, and the continuous tracking of risks until they are negligible. Finally, a relevant example of risk management using the proposed method is illustrated, in which the most appropriate and economical risk management was achieved, and the established objectives of the construction quality and timeline were ensured. This multiphase risk-management approach can be applied to tunnel engineering as well as other engineering fields.