Fig 1.
Coupled relationship between creep and strain-softening of rock surrounding a tunnel.
(a) Evolution law of the plastic zone of rock surrounding a tunnel (b) Rock stress-strain curves and creep trajectory characteristics (c) Rock creep damage and strain-softening process (d) Rock creep curves at different tunnel positions (e) Unloading path of rock surrounding a tunnel.
Fig 2.
Experimental system and rock specimen characteristics after failure.
(a) Experimental loading device and control system (b) Rock specimen characteristics after failure.
Fig 3.
Full stress-strain curves of the mudstone.
Fig 4.
Fitted curves of mudstone strength and softening modulus.
Table 1.
Mudstone strength parameters.
Table 2.
Fitted softening modulus of mudstone.
Table 3.
Stress loading gradients under different confining pressure.
Fig 5.
Creep curves and fitted curves of mudstone under different confining pressures.
(a) σ3 = 0 MPa (b) σ3 = 1 MPa (c) σ3 = 3 MPa(d) σ3 = 7 MPa.
Fig 6.
Viscosity coefficient of mudstone as a function of confining pressure.
Table 4.
Fitted creep parameters of mudstone.
Table 5.
Fitted parameters of viscosity coefficient of mudstone.
Fig 7.
Simplified stress-strain curve of mudstone.
Fig 8.
NBSS creep damage model of mudstone.
Fig 9.
Numerical model and boundary conditions.
Fig 10.
NBSS model curves alongside experimental curves. (a) Steady creep curves (b) Accelerated creep curves.
Fig 11.
Dimensions and boundary conditions of the numerical model.
Fig 12.
Numerical calculation flow chart of the coupled effect of creep and strain-softening.
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Fig 13.
Evolution law of the plastic zone rock surrounding a tunnel (NBMC model).
(a) 100–400 h (b) 500–800 h.
Fig 14.
Evolution law of the plastic zone of rock surrounding a tunnel (NBSS model).
(a) 100–400 h (b) 500–800 h.
Fig 15.
Variation of plastic zone thickness with time.
Fig 16.
Deformation of rock surrounding a tunnel over time.
Fig 17.
Plastic zone distribution characteristics of surrounding rock under anchor rod support.
(a) 100–400 h (b) 500–800 h.
Fig 18.
Anchor rod axial force as a function of time.