Impact of a large and shallow twin-tunnel excavation on a high-speed railway bridge and related protective measures: A case study

Abstract

This case study examines a landmark engineering project in Suzhou, China, involving the construction of two large-diameter (13.2 m) shield tunnels beneath an active high-speed railway (HSR) bridge. This pioneering project is the first of its kind in both China and the world. Advanced numerical simulations were conducted to rigorously assess construction risks. To ensure the operational safety of the existing HSR bridge, an innovative protective system, consisting primarily of segmental steel casing concrete pile barriers, was employed. A comprehensive network of monitoring sensors was strategically deployed to track soil, pile barrier, and pier displacements throughout both the protective and tunnelling phases. Simulation results indicated that tunnelling without protective measures could cause pier displacements of up to 3.1 mm along the bridge—exceeding the maximum allowable displacement of 2 mm in accordance with regulations. Monitoring data revealed that the maximum pier displacement during protective scheme installation was limited to 0.5 mm. With these protective measures, pier displacement during each tunnelling phase remained consistently below 0.5 mm, representing an approximate 80% reduction compared to the unprotected scenario, thereby ensuring the continued safety of the HSR bridge.

Keywords

Large and shallow tunnels / High-speed railway bridge / Tunnel excavation / Numerical simulation / Protective scheme

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

CRediT authorship contribution statement

Wenhui Yang: Validation, Visualization, Conceptualization, Writing - review & editing, Methodology, Writing - original draft, Investigation. Dingwen Zhang: Funding acquisition, Resources, Supervision, Software. Daniela Boldini: Methodology, Software, Writing - review & editing, Supervision.

Declaration of competing interest

Daniela Boldini is an editorial board member for Underground Space and was not involved in the editorial review or the decision to publish this article. All authors declare that there are no competing interests.

Acknowledgement

The authors are grateful for the financial support provided by the China Scholarship Council (CSC, No. 202006090343).

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