Numerical modelling of shotcrete for tunnelling
Author(s)
Schutz, Reinhard
Type
Thesis
Abstract
Shotcrete is a special type of concrete which was invented at the beginning of the 20th century
and is nowadays an important support element for tunnels constructed with the New Austrian
Tunnelling Method (NATM). Immediately after tunnel excavation shotcrete is sprayed onto
the tunnel walls at high pressure in order to provide temporary support. Unfortunately, in the
past very little attention has been given to the development of sophisticated material laws
for shotcrete, since its design and application was mainly based on experience. However,
current design practice, such as that applied in the design of the new Crossrail tunnels,
requires sophisticated modelling of shotcrete behaviour in numerical analysis of tunnel-soil
interaction. Such models are not readily found in the literature, as they have been developed
mainly for structural, rather than geotechnical applications.
In this thesis, a constitutive model for the time-dependent behaviour of shotcrete has been
developed within the framework of elasto-plasticity. Two independent yield surfaces control
the behaviour of shotcrete in multiaxial loading conditions for both compression and tension.
The model formulation is based on strain hardening/softening plasticity, where the expansion
and contraction of the yield surfaces are governed by normalised plastic strains. Cracking
of the shotcrete is considered within the smeared crack concept. Furthermore, the proposed
material law includes the time-dependency of stiffness and strength behaviour. The reducing
deformability of the shotcrete during cement hydration has been taken into account. The
model has been extended to account for creep, shrinkage and hydration temperature induced
deformations at early shotcrete ages. After a robust implementation into the Imperial College
Finite Element Program (ICFEP), model calibration and validation have been performed for
shotcrete experiments taken from the literature. The developed constitutive model has then
been applied to the analysis of a typical tunnel construction in London Clay, modelling the
early age material properties of the shotcrete tunnel lining in detail for various excavation
schemes. Finally, it has been shown that the proposed constitutive model is capable of
reproducing the complex behaviour of young shotcrete at early ages and can be applied
successfully to boundary value problems in geotechnical engineering.
and is nowadays an important support element for tunnels constructed with the New Austrian
Tunnelling Method (NATM). Immediately after tunnel excavation shotcrete is sprayed onto
the tunnel walls at high pressure in order to provide temporary support. Unfortunately, in the
past very little attention has been given to the development of sophisticated material laws
for shotcrete, since its design and application was mainly based on experience. However,
current design practice, such as that applied in the design of the new Crossrail tunnels,
requires sophisticated modelling of shotcrete behaviour in numerical analysis of tunnel-soil
interaction. Such models are not readily found in the literature, as they have been developed
mainly for structural, rather than geotechnical applications.
In this thesis, a constitutive model for the time-dependent behaviour of shotcrete has been
developed within the framework of elasto-plasticity. Two independent yield surfaces control
the behaviour of shotcrete in multiaxial loading conditions for both compression and tension.
The model formulation is based on strain hardening/softening plasticity, where the expansion
and contraction of the yield surfaces are governed by normalised plastic strains. Cracking
of the shotcrete is considered within the smeared crack concept. Furthermore, the proposed
material law includes the time-dependency of stiffness and strength behaviour. The reducing
deformability of the shotcrete during cement hydration has been taken into account. The
model has been extended to account for creep, shrinkage and hydration temperature induced
deformations at early shotcrete ages. After a robust implementation into the Imperial College
Finite Element Program (ICFEP), model calibration and validation have been performed for
shotcrete experiments taken from the literature. The developed constitutive model has then
been applied to the analysis of a typical tunnel construction in London Clay, modelling the
early age material properties of the shotcrete tunnel lining in detail for various excavation
schemes. Finally, it has been shown that the proposed constitutive model is capable of
reproducing the complex behaviour of young shotcrete at early ages and can be applied
successfully to boundary value problems in geotechnical engineering.
Date Issued
2010-02
Date Awarded
2010-06
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Potts, David
Sponsor
Geotechnical Consulting Group (GCG) London
Creator
Schutz, Reinhard
Publisher Department
Civil and Environmental Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)