Ground movements due to deep excavations in Shanghai: Design charts

Abstract

Recent research has clarified the sequence of ground deformation mechanisms that manifest themselves when excavations are made in soft ground. Furthermore, a new framework to describe the deformability of clays in the working stress range has been devised using a large database of previously published soil tests. This paper aims to capitalize on these advances, by analyzing an expanded database of ground movements associated with braced excavations in Shanghai. It is shown that conventional design charts fail to take account either of the characteristics of soil deformability or the relevant deformation mechanisms, and therefore introduce significant scatter. A new method of presentation is found which provides a set of design charts that clarify the influence of soil deformability, wall stiffness, and the geometry of the excavation in relation to the depth of soft ground.

Graphical abstract

Keywords

Shanghai / excavations / mobilizable strength design / dimensionless groups / design charts

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Acknowledegements

The authors would like to thank Dr. Xu and Prof. Wang for sharing information about their database of Shanghai excavation data – without which this paper would not have been possible. Thanks are also due to Mr. Qing Li for performing the triaxial tests on the Shanghai clay samples, and to Dr. Yuchen Li and Miss Yu Ge for assisting with the translation of some Chinese language material. Finally, we are grateful to the reviewers of the paper for their helpful comments and suggestions.

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