CUED Publications database

Semi-analytical prediction of ground movements due to shallow tunnels in sand

Franza, A and Marshall, AM (2015) Semi-analytical prediction of ground movements due to shallow tunnels in sand. In: UNSPECIFIED pp. 461-466..

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© The authors and ICE Publishing: All rights reserved, 2015. In engineering practice, tunnelling-induced ground movements are often described by empirical formulas. Recent research has shown that simple empirical relationships do not predict the change in settlement trough shape that occurs in sands as tunnel volume loss increases. In this paper, a closed-form solution is developed to assess the greenfield displacements around shallow tunnels in sand. An elastic analytical solution for incompressible soil is modified through a corrective term, which is a function of the spatial coordinates and tunnel volume loss. The elastic solution allows modelling of the tunnel deformation mechanism through a volume loss and ovalization term. The corrective term aims to account for the effect of non-linear behaviour and volumetric strains on the resulting settlement trough shape. One plane-strain centrifuge test performed on tunnels in dry silica sand is used to define a relationship for the tunnel deformation parameters (ground loss and ovalization) and to calibrate the coefficients of the corrective term. The results highlight the main effects of volume loss on the ground movement patterns. Furthermore, the outcomes illustrate that closed-form solutions developed for clay may not be applicable in sands. An expression to estimate vertical and horizontal displacements for shallow tunnels in sands is proposed, which may provide useful guidance to tunnel design engineers.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Divisions: Div D > Structures
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:34
Last Modified: 22 May 2018 08:21