Product category:
Drainage, Footings and Piling
News Release from: Bachy Soletanche | Subject: Concrete circular shaft at Canary Wharf
Edited by the Buildingtalk Editorial
Team on 14 March 2008
Bachy Soletanche construct 47m deep
circular shaft
Leading geotechnical specialist, Bachy Soletanche has recently constructed a concrete circular shaft at London's business district, Canary Wharf.
The ground engineering specialist has created the reinforced concrete diaphragm wall at Canary Wharf's North Quay due to the shaft's depth of 47m In order to retain verticality while the shaft is constructed, BSL required the use of a KS grab which has been sent across from Soletanche Bachy's HQ in France especially for the project
This article was originally published on Buildingtalk on 5 Feb 2007 at 8.00am (UK)
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Barry Osborn, operations manager from Bachy Soletanche Limited explained: "For some of our recent diaphragm wall projects we have used the rope operated grab to install the panels, but the walls had depths of less than 30m".
"With the North Quay shaft requiring a deeper 47m depth, we decided to utilise the KS grab".
"This is a hydraulic grab designed and manufactured by Soletanche Bachy which is fitted with instrumentation allowing verticality correction, and therefore, an ideal solution for the North Quay shaft project." The diaphragm wall at North Quay was constructed using the slurry trench technique.
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This involves excavating a narrow trench that is kept full of an engineered fluid - bentonite mud.
The fluid exerts hydraulic pressure against the trench walls and acts as a shoring to prevent collapse.
The first stage in creating the diaphragm wall requires the construction of a guide wall trench.
To maintain the accuracy of the shaft construction of the North Quay shaft, the guide wall is constructed to a depth of one metre.
Once this stage is complete, the panel excavation can progress.
The circular diaphragm wall shaft is installed in five separate sections or 'panels'.
Each 'panel' is 1200mm in width and constructed using the KS grab.
Each panel consists of three "bites" of the 2.8m wide grab - a "virgin" bite, a "stop-end" bite and a "centre bite".
When these three bites are complete, each panel is approximately 5.6m in length.
In order to form joints between primary and secondary 'panels', stop end casings are placed at both ends of the primary 'panel'.
These stop ends are then withdrawn once the concreting of the primary panel is complete.
Barry Osborn continued: "With the diaphragm wall being excavated to such a large depth, we have to ensure that every stage is completed with great accuracy, including the panels' verticality and width of trench".
"The KS grab is a great benefit for these quality control checks as its accompanying monitoring equipment can identify the slightest movement." BSL is acting as a principal contractor for EDF Energy Networks, who requires the use of a circular secant shaft as part of a cable tunnel project, delivering essential electricity network reinforcement in East and Central London.
The nine metre internal diameter shaft will provide an opening for a tunnel boring machine (TBM) to enable it to be lowered into the ground and complete future tunnelling works.
It will also create a general access point for EDF Energy Networks' engineers".
"When taking on the role of a key contractor, we have to coordinate a range of other site essentials, such as crane hire and security." Barry Osborn explained.
With the initial construction of the diaphragm wall complete, BSL continued works by capping the wall and installing a platform for future works to continue.
Completion on BSL's contract was at the end of January.
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