A review of seismic resilience of shield tunnels

Considering the increasingly complex and interconnected subway tunnels linking cities, this review argues that the overall reliability of tunnel engineering is crucial for protection when subjected to loads caused by major catastrophes, particularly earthquakes. Therefore, the key topic of this paper is the application of the resilience concept for shield tunnel structure seismic resilience assessment. In the review, from the technical perspective of civil engineering, based on the five characteristics of resilience, four aspects regarding the seismic resilience of shield tunnels were presented: failure mode and damage mechanism, seismic design method, prevention mea-sures and post-earthquake repair of shield tunnels. First, the definition of seismic resilience of shield tunnel is introduced. Then the failure modes of the shield tunnel under the seismic action and mechanism of damage were summarised under two types: global and local. Consequently, based on the design, several seismic calculation methods were analysed. Next, the current understanding and exploration of shield tunnels in the construction and repair stages were described. Because of lack of relevant repair cases following earthquakes, this review provides a summary of the newly developed techniques and methods of the shield tunnel, which are used to improve seismic resilience during operation. Further, the limitation of the current research were summarised, followed by a short discussion on improving the resilience of shield tunnels in terms of seismic design, con-struction, operation, and post-earthquake repairs. The final aim is to develop a robust and suitable tool to enhance and maintain shield tunnel resilience, starting from the weaknesses of the tunnel structure faced with earthquakes.