Study on Evolution of Surrounding Rock Stability and Structural Mechanical Behavior During In-Situ Expansion of Existing Tunnels in Weak Rock Mass Zhejiang Institute of Communications Company Limited Hangzhou, Chin

Format:

Book

Conference/Event

Author/Creator:

Zheng, Xiaoqing, author.

Contributor:

Chen, Chuan

Chen, Tao

Huo, Xinwang

Kang, Xiaoyue

Xu, Kai

Conference Name:

2025 8th International Conference on Traffic Transportation and Civil Architecture (ICTTCA 2025) (2025-04-18 : Tianjin, China)

Language:

English

Physical Description:

1 online resource cm

Place of Publication:

Warrendale, PA SAE International 2025

Summary:

To address the escalating traffic demands and tackle the complex mechanical challenges inherent in in-situ tunnel expansion, this study, grounded in the Huangtuling Tunnel project in Zhejiang Province, China, focuses on the stability evolution of surrounding rock and the mechanical characteristics of structures during the in-situ expansion of existing tunnels under weak surrounding rock conditions. By systematically comparing core post-excavation featuressuch as surrounding rock displacement fields, ground pressure distribution pat-terns, and mechanical responses of support structuresbetween newly constructed tunnels and in-situ expanded tunnels, the research reveals key mechanical principles governing the construction of large-section tunnels in weak rock formations. Specifically, the findings are as follows: (1) Both newly constructed and in-situ expanded large-section tunnels exhibit significant spatial heterogeneity in surrounding rock deformation. The vault-spandrel zones serve as the primary deformation-concentrated areas, with displacement magnitudes 3 to 5 times those of the sidewalls, where displacement is near-ly negligible. This pronounced spatial differentiation in deformation patterns confirms the necessity of treating vault deformation monitoring and control as core indicators in formulating stability evaluation criteria for large-section tunnels. This has direct implications for optimizing construction methods, such as prioritizing the reinforcement of initial support for the vault during stepwise excavation. (2) The overall stability of surrounding rock in in-situ expanded tunnels is inferior to that of newly constructed large-section tunnels, accompanied by distinct asymmetric deformation characteristics. However, the peak additional displacement induced by expansion excavation is significantly smaller than the initial displacement during new tunnel construction, potentially attributed to the pre-constraining effect of the existing tunnel structure on the surrounding rock. (3) Stress redistribution during tunnel in-situ expansion leads to a significant pressure difference within the surrounding rock. The surrounding rock pressure on the expansion side is 30%-40% higher than on the opposite side, resulting in a strongly asymmetric distribution. This biased pressure subjects support structures on the expansion side to greater axial forces and bending moments, increasing the risk of structural damage due to uneven loading. This highlights the need to enhance the stiffness of support systems on the expansion side in design, such as extending anchor lengths or increasing the density of steel arches

Notes:

Vendor supplied data

Publisher Number:

2025-99-0207

Access Restriction:

Restricted for use by site license