Investigation of shield face stability by transparent soil models

M. Ahmed, M. Iskander

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Reliable face support pressure is necessary for shield driven tunnels in cohesionless soils to prevent excessive ground movements. This paper presents experimental work on stability of a tunnel face using transparent soil models aiming to obtain magnitude of tunnel face minimum supporting pressure, failure pattern and extension of failed zone. A model tunnel was preinstalled in transparent soil which was supported at the face by means of water pressure. Tests were performed by reducing supporting pressure until collapse occurred. Model tests were sliced optically with laser sheet and images were captured for every decrement in tunnel supporting pressure. Later, these images were analysed by digital image correlation (DIC) and vector fields of incremental displacements were obtained. Values of minimum support pressures were given for different cover/diameter (C/D) ratios. Geometry of the failure zones depicted for different (C/D) values and appeared to be of chimney shape with a limited extension front of the face. A minimum support pressure was achieved with support pressures as low as 10 ± 1 percent of the effective vertical stress at the tunnel axis. The stability of the tunnel face was related to the coefficient of active earth pressure with C/D ratio having a small effect on the magnitude of required pressure at collapse. In general, results of the study were in agreement with current knowledge of full-scale situations.

Original languageEnglish (US)
Title of host publication14th Australasian Tunnelling Conference 2011
Subtitle of host publicationDevelopment of Underground Space, Proceedings
Pages329-336
Number of pages8
StatePublished - 2011
Event14th Australasian Tunnelling Conference 2011: Development of Underground Space - Auckland, New Zealand
Duration: Mar 8 2011Mar 10 2011

Publication series

Name14th Australasian Tunnelling Conference 2011: Development of Underground Space, Proceedings

Other

Other14th Australasian Tunnelling Conference 2011: Development of Underground Space
CountryNew Zealand
CityAuckland
Period3/8/113/10/11

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction

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