Abstract
This study investigated the behavior of a 38-m deep twin circular peanut-shaped cofferdam interconnected with a rectangular section for cut-and-cover tunnel construction using distributed fiber-optic sensors (DFOSs) based on optical frequency domain reflectometry (OFDR). The distributed sensors revealed that temperature changes on the two sides of the diaphragm wall were different upon its exposure by excavation, while the measured strains were used to evaluate the wall deflection and bending moments. The high spatial resolution achieved by DFOS measurements revealed unique aspects of the wall response, which are difficult to obtain by conventional types of instrumentation. In particular, the strains along vertical and lateral directions of the wall panels were measured, the latter of which indicated eccentric compression in the concrete panels that arises from the distinctive peanut-shaped geometry. Developments of hoop forces and circumferential bending moments in the panels at various construction stages are discussed, with particular focus on the release of such during partial demolition of a temporary cross wall to facilitate the assembly and launching of tunnel boring machines. The mechanisms of stress developments and release were simulated using three-dimensional finite-element models that, together with the field measurements, enhance the understanding of the behavior of multicell cofferdams.
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Data Availability Statement
All monitoring data and numerical results that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
This paper is published with the permission of the Director of Civil Engineering and Development, the Head of the Geotechnical Engineering Office, and the Project Manager of the East Development Office of the Government of the Hong Kong SAR, China. The work presented in this paper is supported by Research Impact Fund (RIF) project (R5037-18), a Theme-based Research Scheme Fund (TRS) project (T22-502/18-R), and four General Research Fund (GRF) projects (PolyU 152179/18E; PolyU 152130/19E; PolyU 152100/20E; 15222021) from the Research Grants Council (RGC) of the Hong Kong Special Administrative Region Government of China. The authors also acknowledge the financial supports from grants (CD82 and CD7A) from the Research Institute for Land and Space, and grants (ZDBS, BD8U) from the Hong Kong Polytechnic University.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 149 • Issue 12 • December 2023
Copyright
© 2023 American Society of Civil Engineers.
History
Received: Jul 25, 2022
Accepted: Jul 21, 2023
Published online: Sep 28, 2023
Published in print: Dec 1, 2023
Discussion open until: Feb 28, 2024
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