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Considerations for monitoring of deep circular excavations

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Schwamb, T 
Elshafie, MZEB 
Soga, K 
Mair, RJ 

Abstract

jats:p Understanding the magnitude and distribution of ground movements associated with deep shaft construction is a key factor in designing efficient damage prevention/mitigation measures. Therefore, a large-scale monitoring scheme was implemented at Thames Water's 68 m deep Abbey Mills Shaft F in East London, UK, constructed as part of the Lee Tunnel Project. The scheme comprised inclinometers and extensometers which were installed in the diaphragm walls and in boreholes around the shaft to measure deflections and ground movements. However, interpreting the measurements from inclinometers can be a challenging task, as it is often not feasible to extend the boreholes into ground unaffected by movements. The paper describes in detail how the data are corrected. The corrected data showed very small wall deflections of less than 4 mm at the final shaft excavation depth. Similarly, very small ground movements were measured around the shaft. Empirical ground settlement prediction methods derived from different shaft construction methods significantly overestimate settlements for a diaphragm wall shaft. The results of this study will help to inform future projects, such as the forthcoming 25 km long Thames Tideway Tunnel with its 18 deep shafts being constructed adjacent to existing infrastructure. </jats:p>

Description

Keywords

excavation, field testing & monitoring, geotechnical engineering

Journal Title

Proceedings of the Institution of Civil Engineers: Geotechnical Engineering

Conference Name

Journal ISSN

1353-2618
1751-8563

Volume Title

Publisher

Thomas Telford Ltd.
Sponsorship
Engineering and Physical Sciences Research Council (EP/I019308/1)
Engineering and Physical Sciences Research Council (EP/K000314/1)
Engineering and Physical Sciences Research Council (EP/L010917/1)
Engineering and Physical Sciences Research Council (EP/N021614/1)
Engineering and Physical Sciences Research Council