Distributed Fibre Optic Sensing of a Deep Excavation Adjacent to Pre-existing Tunnels. Issue 3 (18th June 2018)

• Record Type: Journal Article
• Authors: Li, Z.; Soga, K.; Kechavarzi, C.
• Is Part Of: Géotechnique letters. Volume 8:Issue 3(2018)
• Page Start: 1
• Page End: 24
• Publication Date: 2018-06-18
• Subjects: Distributed fibre optic sensing -- Diaphragm wall -- wall-tunnel interaction -- Top-down excavation -- Pre-existing tunnel; Geotechnical engineering -- Periodicals; Engineering geology -- Periodicals; 624.151
• DOI: 10.1680/jgele.18.00031
• Languages: English
• ISSNs: 2045-2543

Abstract

Abstract : This paper investigated a diaphragm wall behaviour due to deep excavation at Paddington tunnel station site in London clay. The Paddington site was the only train station in the Crossrail project constructed using a top-down excavation, and it provided the opportunity to evaluate the effect of a pre-existing tunnel on D-wall behavior using distributed fibre optic sensing (DFOS) for the first time. Distributed fibre optic cables were embedded in diaphragm wall panels to monitor the changes in strain conditions during three key stages of construction; tunnel passage, concourse excavation and base excavation. After station construction, relevant finite element analysis was conducted to evaluate the D-wall performance during excavation, and the computed results were compared against the field measurements recorded by embedded DFOS in the D-wall as well as the ground inclinometers. The DFOS measurements depicted the D-wall behaviour in agreement with the conventional inclinometer method and finite element results, demonstrating its feasibility in monitoring underground earth retaining infrastructure. A comparison between the diaphragm wall behaviour with pre-existing tunnels at Paddington site and that of the same wall without tunnel allows providing some guidance for the design and construction of retaining structures adjacent to pre-existing tunnels.