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On the non‐linear ‘squeezing’ effects around circular tunnels
Author(s) -
Gioda Giancarlo
Publication year - 1982
Publication title -
international journal for numerical and analytical methods in geomechanics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.419
H-Index - 91
eISSN - 1096-9853
pISSN - 0363-9061
DOI - 10.1002/nag.1610060104
Subject(s) - creep , viscoplasticity , stiffness , geotechnical engineering , rheology , finite element method , stress (linguistics) , viscosity , excavation , structural engineering , mechanics , geology , engineering , materials science , constitutive equation , physics , composite material , linguistics , philosophy
An analysis is presented of the non‐linear creep effects around a deep circular tunnel driven in ‘squeezing’ ground. The time‐dependent behaviour of the geotechnical medium is described by means of a simple viscoplastic rheological model capable of approximating primary, secondary and tertiary creep behaviours. It is shown that tertiary creep can be allowed for by providing a suitable law governing the variation of some material parameters (such as viscosity) with stresses and strains. The basic operations of the ‘evolutive’ procedure adopted for time integration are outlined. Along each time integration step, quadratic variations of the stress and strain fields and linear variations of the material parameters are assumed. The results of various finite element analyses are presented concerning both lined and unlined cases. For the lined cases, the influence of the liner stiffness and of the time elapsed between the end of excavation and the liner installation is considered.