Modelling and assessing lifetime resilience of underground infrastructure to multiple hazards: Toward a unified approach

Underground infrastructures are the essential assets to the transport, energy storage, and utilities. However, with the deepening development of urbanisation and modernisation, the safety of underground infrastructure is threatened by various natural or human-induced hazards. In the construction and operation phases, hazards can be single, cascade or combined in their origin and effects, the combined or potential interrelated effects of them may exacerbate consequences, leading to higher loss of functionality and cost of restoration. Determining the post-hazard capacity and recovery ability of these infrastructures in a quantitative approach remains ongoing research priority. This paper proposes a unified approach of implementing a quantified resilience assessment of underground infrastructures subjected to multiple hazards. Embedding potential abrupt hazards into long-term deterioration of a circular tunnel, coupled with modelling of restoration, the lifecycle performance is presented. The results show that the disturbance caused by excavation construction has an influence on the performance of subsequent operation phase. The deterioration hazards including ageing and corrosion of structure and creep deformation of rock mass during the whole service life continuously decreases the functionality of the tunnel. While abrupt hazards, such as earthquake and blasting, lead to a sharp decline in functionality in a short period of time. Continuous evolution over time of deformation and damage caused by various hazards, whether deteriorated or abrupt, will be inherited and accumulated. Timely repair, such as pretensioned bolts and grouting can effectively restore the bearing capacity of the infrastructure to a specific extent. Through this numerical approach, the restoration time can be estimated by the functionality recovered and unit consumed time. The dimensionless resilience index is then calculated for the post-hazard functionality based on the specific hazard scenarios and restoration solutions.