Temporary propping of deep excavations - guidance on design (C517)

Demand is rising for buildings with more basement space, highway underpasses and rapid transit lines, all of which require excavation propping systems. Different methods for calculating prop loads have led to significant variation in these temporary works. There is a need, therefore, for a clear and authoritative statement on the practical limits to which ground movements can be restricted. This book provides guidance on the design of temporary propping systems for deep excavations with the aim at improving efficiency in their use while ensuring safety. It proposes a new empirical method for establishing temporary prop loads for design, developed from the Peck approach and based on a comprehensive survey of field measurements of prop loads. Distributed prop load diagrams, derived from analyses of the measured loads, are provided, from which prop loads may be obtained. The application of this distributed prop load method is explained, illustrated by worked examples. The guidance covers single and multi-propped excavations of varied geometry, flexible and stiff walls, and the range of ground conditions found in the UK. It considers temperature effects, buildability, use of the Observational Method, instrumentation of props, and choice of temporary propping systems. Other subjects covered include contractual arrangements, performance requirements, allocation of responsibility and the overall legal context. Current methods of determining the prop load and of design are reviewed, and the book concludes with a summary of recommendations. This title is a valuable addition to the libraries of temporary works designers, geotechnical engineers, project managers and clients.

Key words: health and safety, ground engineering, design and buildability.

ISBN: 978-0-86017-517-9

Author: D Twine and H Roscoe

Number of pages: 224 (paperback)

Publisher: CIRIA

Date of Publication: December 1999