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Prop loads in large braced excavations (PR77)

Embedded walls retaining the sides of large excavations are often supported at some stage in the construction process by temporary props at one or more levels, in order to reduce wall and ground movements. The provision of temporary props is costly in terms of money and time, and there may be risk to the site operatives installing and removing them.

This publication presents the findings of an EPSRC and industry-funded research project that measured and analysed the loads in the temporary props at the Canada Water and Canary Wharf station excavations. There is a widely held view within the construction industry that the procedures currently used in design tend to overestimate actual prop loads. The main aim of the research was to investigate the reasons for this apparent discrepancy by monitoring the temporary prop loads at Canada Water and Canary Wharf. Prop temperatures were also measured to assess their influence on prop loads. Both case studies involved stiff, reinforced concrete walls in mixed ground, and provided a unique opportunity to investigate the significance of the effects of prop loads in practice. This publication, being a research summary, will be a help to temporary works designers and geotechnical engineers. It accompanies CIRIA publication C517 Temporary propping of deep excavations - guidance on design.

Key words: ground engineering.

ISBN: 978-0-86017-877-4
Author: W Powrie and M Batten
Number of pages: 36 (paperback)
Publisher: CIRIA
Date of Publication: February 2000