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Computational Science, Engineering & Technology Series
ISSN 1759-3158
Edited by: B.H.V. Topping
Chapter 11

Numerical Models in Soft Ground Tunnelling

C.E. Augarde

School of Engineering, University of Durham, United Kingdom

Full Bibliographic Reference for this chapter
C.E. Augarde, "Numerical Models in Soft Ground Tunnelling", in B.H.V. Topping, (Editor), "Progress in Civil and Structural Engineering Computing", Saxe-Coburg Publications, Stirlingshire, UK, Chapter 11, pp 285-314, 2003. doi:10.4203/csets.10.11
Keywords: tunnelling, finite element analysis, SCL, numerical models.

Numerical modelling has been used for a number of years for problems relating to soft-ground tunnelling (i.e. where the ground being excavated is not rock). Three problems require solutions in soft ground tunnelling. Firstly the effects tunnelling will have on the surroundings are determined. Secondly, the stability of the works during and after construction must be assessed. The third problem is the design of the tunnel permanent lining. This chapter will cover aspects of the first two problems only.

The first problem, that of determining the effects of tunnelling, is a major area of interest in the UK and elsewhere. The motivation is the increasing number of new tunnels proposed for urban areas. Installation of a tunnel in soft ground inevitably leads to movement of the surface above, particularly if the tunnel is shallow (i.e. having a depth of cover up to 30m). Semi-empirical techniques have been developed in the past to predict these movements. However, these methods have the drawback that they cannot adequately deal with the presence of structures on the surface which themselves change the movement pattern due to their stiffness and weight.

Recent research has led to the development of models that include more accurate modelling of soil behaviour, particularly for clays, and simulation of modern tunnelling techniques such as sprayed concrete lining. Some of this recent modelling is reviewed here.

Assessing stability is commonly approached using analytical approaches, which have been developed from empirical rules, or through the use of plasticity approaches. Of more interest to computational researchers are quasi-finite element techniques also based on classical plasticity. The use of these methods on collapse problems in tunnelling by the author is demonstrated in this chapter.

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