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Effects of Creep on Shield Tunnelling Through Squeezing Ground
Thomas Leone1, Alexandros N Nordas1, Georgios Anagnostou1
1ETH Zurich, Zurich, Switzerland.
Rock Mechanics and Rock Engineering
|January 8, 2024
Summary
Creep significantly impacts shield jamming and lining damage risk in squeezing ground. Numerical simulations show creep can increase shield loading during advance and is unfavorable during standstills, contradicting common assumptions.
Area of Science:
- Geotechnical Engineering
- Tunnelling Engineering
- Rock Mechanics
Background:
- Assessing shield jamming and lining damage in squeezing ground is critical for tunnelling projects.
- Existing models often overlook the time-dependent effects of ground creep on rock pressure evolution.
Purpose of the Study:
- To enhance the reliability of risk assessment for shield jamming and lining damage.
- To analyze the influence of ground creep on rock pressure over time during mechanised tunnelling.
Main Methods:
- Numerical simulations of mechanised tunnelling, including shield advance and standstill phases.
- Application of a linear elastic-viscous plastic constitutive model based on Perzyna's overstress theory.
- Investigation of time-dependent plastic deformations using a viscosity parameter.
Main Results:
- Shield loading during advance can increase with viscosity, challenging the view that creep is always favorable for shield jamming.
- Creep is detrimental during long standstills and for long-term lining integrity due to accumulated viscoplastic deformations.
- Simplified continuous excavation models underestimate shield loading during standstills.
Conclusions:
- The time-dependent nature of creep must be considered for accurate risk assessment in squeezing ground tunnelling.
- Explicit simulation of standstill periods is necessary for reliable shield loading and lining damage evaluation.
- The study validates a semi-discrete modelling approach for tunnel construction analysis.
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