Managing Inverted Arch Heaving in Sanlian Tunnel: Analysis of Inverted Arch Structure Utilizing Prestressed Anchor Rods

• Published in: Geotechnical and Geological Engineering
• Main Author: Wang Y.; Krishta David T.; Mansor H.; Guan J.
• Format: Article
• Language: English
• Published: Springer Science and Business Media Deutschland GmbH 2024
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85189682339&doi=10.1007%2fs10706-024-02792-7&partnerID=40&md5=e22d604e7ad21c276043660fe62f784c

The inverted arch heaving is detrimental to the structural safety of tunnels and can cause operational accidents. It is necessary to perform the research on maintenance strategies of inverted arch heaving to ensure the structural safety of tunnels. This paper took the Sanlian Tunnel in Southwest China as the engineering background, and the goals of this research were to explore the cause and maintenance of the inverted arch heaving in tuff stratum. The research methodology in this paper includes numerical simulation and field observations. Proposing maintenance measures for inverted arch heaving in tuff formation and grasping the long-term stress characteristics of the inverted arch structure are the contributions of this study. The inverted arch distress includes heaving (85 mm), cracks, and flexural deformation of reinforcements. FLAC3D numerical simulation shows that the continuous deformation because of the tuff rheological effect has an adverse impact on the inverted arch structure, resulting in cracking and heaving. Deepened inverted arch structure by 65 cm combined with 8 m-long prestressed anchor rods were adopted to control the distress. The effectiveness of the maintenance approach was assessed through field observations lasting for three years. Influenced by the long-term rheology of the tuff, the stresses in the inverted arch increased rapidly at first, then slowly, and gradually stabilized two years after the construction was completed. The maximum stress of prestressed anchor rods, steel arch frames, initial support concrete, and secondary lining concrete were 84.53 MPa, 22.40 MPa, 13.35 MPa, 7.20MP, respectively, which were less than the allowable stress (namely 210 MPa, 160 MPa, 23.8 MPa, 32.5 MPa, respectively). Furthermore, the minimum safety factor (namely 6.75) of the reinforced inverted arch met the requirements (>2.4) specified by the Code for Design of Railway Tunnel. The reported findings validate the overall safety of the inverted arch structure following the implementation of control measures, demonstrating the efficacy of these measures in effectively addressing the identified issues. The proposed maintenance strategies and revealed long-term stress characteristics of inverted arch structure in this work can be referenced for construction of tunnels in tuff formation. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.