Abstract
AbstractThis contribution deals with numerical modelling of drill‐and‐blast tunnelling. Special attention is paid to the modelling of a shotcrete layer supporting the surrounding rock after excavation. Due to an increasing load caused by further tunnel advance, and due to shrinkage caused by hydration which is restrained by the surrounding rock, the shotcrete is loaded in place at a very early age. Hence it is required to accurately model the evolution of its strength and stiffness. This is done using a fully coupled hygro‐thermo‐chemo‐mechanical multi‐phase model for the shotcrete. Creep of shotcrete is taken into account using a microprestress‐solidification approach. The constitutive model for the shotcrete is calibrated using experimental data obtained from laboratory tests reported in literature. The setup for the tunnelling simulation is completed assuming elastic‐plastic response for the surrounding rock and the additional steel anchors. The results of this contribution are considered to be a further step towards a more accurate modelling of excavation procedures in conventional drill‐and‐blast tunnelling.
Highlights
The load exerted by the surrounding rock on a cross section with installed shotcrete lining does increase with increasing distance to the tunnel face
This is due to the fact that close to the tunnel face, the load caused by the overburden is carried by the rock and lining in a two-dimensional way
A reduction of this load by 85% is assumed to yield the initial state for the simulation at which the 20cm thick shotcrete shell and the 12 rock bolts are installed
Summary
Shotcrete is used to secure the tunnel surface. Once the shotcrete is hardened, it forms a shell-like tunnel lining supporting the surrounding rock. The load exerted by the surrounding rock on a cross section with installed shotcrete lining does increase with increasing distance to the tunnel face.
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