Experimental investigation of the face stability of shallow tunnels in sand |
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| Authors: | Ansgar Kirsch |
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| Institution: | (1) Division of Geotechnical and Tunnel Engineering, University of Innsbruck, Technikerstr. 13, 6020 Innsbruck, Austria;(2) Present address: ILF Consulting Engineers, Feldkreuzstr. 3, 6063 Rum/Innsbruck, Austria |
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| Abstract: | Various models have been proposed for the prediction of the necessary support pressure at the face of a shallow tunnel. To
assess their quality, the collapse of a tunnel face was modelled with small-scale model tests at single gravity. The development
of the failure mechanism and the support force at the face in dry sand were investigated. The observed displacement patterns
show a negligible influence of overburden on the extent and evolution of the failure zone. The latter is significantly influenced,
though, by the initial density of the sand: in dense sand a chimney-wedge-type collapse mechanism developed, which propagated
towards the soil surface. Initially, loose sand did not show any discrete collapse mechanism. The necessary support force
was neither influenced by the overburden nor the initial density. A comparison with quantitative predictions by several theoretical
models showed that the measured necessary support pressure is overestimated by most of the models. Those by Vermeer/Ruse and
Léca/Dormieux showed the best agreement to the measurements. |
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