New Viscoplastic Model for Design Analysis of Tunnels in Squeezing Conditions |
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| Authors: | D Debernardi G Barla |
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| Institution: | (1) Department of Structural and Geotechnical Engineering, Politecnico di Torino, Torino, Italy |
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| Abstract: | Summary This paper is intended to describe the SHELVIP (Stress Hardening ELastic VIscous Plastic) model, a new viscoplastic constitutive
law which has been developed to incorporate the most important features of behaviour observed in tunnels excavated in severe
to very severe squeezing conditions. This model couples the elastoplastic and time-dependent behaviour by using a plastic
yield surface, as frequently adopted in tunnel design analysis, and the definition of a state of overstress referred to a
viscoplastic yield surface. The model is formulated in all its detailed aspects. The related analytical closed-form solution
for representing triaxial creep deformations is developed. Also developed is an incremental numerical solution for describing
the triaxial stress–strain behaviour under constant strain rate conditions. The model is shown to fit very satisfactorily
the results of creep tests on clay shales and relaxation tests on coal specimens, as recently performed for design analysis
of tunnels in squeezing conditions.
Correspondence: D. Debernardi, Department of Structural and Geotechnical Engineering, Politecnico di Torino, Torino, Italy |
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| Keywords: | : Constitutive laws squeezing conditions time-dependent behaviour viscoplastic behaviour creep relaxation |
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