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Durham University

Department of Engineering

Staff Profile

Publication details for Dr Ashraf Osman

Osman, A. S., Bolton, M. D. & Mair, R.J. (2006). Predicting 2D ground movements around tunnels in undrained clay. Géotechnique 56(9): 597-604.

Author(s) from Durham

Abstract

A new analytical method is introduced for calculating
displacements due to tunnelling. This is conceived within
the framework of the bound theorems of plasticity, but
allowing for soil strain-hardening. The ground displacements
due to tunnelling are idealised by a simple displacement
mechanism of distributed shearing in the plane of
the tunnel cross-section. The tunnel support pressure
corresponding to a certain volume loss is calculated from
energy balances of the work dissipated in distributed
shear, the potential energy loss of soil flowing into the
tunnel, and the work done by this soil against the tunnel
support pressure. The calculations are carried out in
steps of small volume loss accompanying small reduction
in support pressure, after each of which the tunnel
geometry is updated. In this way, each reduced tunnel
support pressure is related to a complete ground displacement
field. A simplified closed-form solution is also
provided for the prediction of maximum surface ground
settlement for the particular case of deep tunnelling. This
closed-form solution is obtained by integrating the vertical
equilibrium equation on the tunnel centreline from
the tunnel crown up to the ground surface. These two
analytical solutions have been validated against five previously
published centrifuge tests.

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