The classical Nishihara model can better describe the attenuation of the creep process in the rocks and the deformation characteristics of the creep stage at constant speed. However, since the components used in the Nishihara model are ideal linear components, it is difficult to describe the law of nonlinear rock deformation at the accelerated creep stage.^{19,20,21}. However, creep failure at the accelerated creep stage may better characterize the entire rock creep process.^{22,23,24}. Therefore, based on the Nishihara model shown in FIG. 6the author introduced a nonlinear elastomer and an injury variable *D* and developed a new model of nonlinear shear shear damage as shown in FIG. 7.

### Elastomers

Liu et al.^{25} developed an elastomer creep equation,

$$ \ varepsilon_ {1} = \ frac {\ tau} {{k_ {1}}} $$

(1)

where *τ* is the shear stress of the elastomer, *k*_{1} is the modulus of elasticity of the elastomer and *ε*_{1} is the deformation of the elastomer.

### Nonlinear elastomer

Wang et al.^{26} defined a new nonlinear function as follows:

where *you* is an independent variable *f*

(3)

where *k*_{20} is the initial value of the modulus of elasticity of the nonlinear elastomer, *k*_{2} is the modulus of elasticity of a nonlinear elastomer.

The constitutional equation for a nonlinear elastomer is

$$ \ varepsilon_ {2} = \ frac {\ tau} {{k_ {2}}} $$

(4)

where *τ* is the shear stress of the nonlinear elastomer, *k*_{2} is the modulus of elasticity of the nonlinear elastomer and *ε*_{2} is the deformation of a nonlinear elastomer. The creep equation for a nonlinear elastomer is determined as follows:

$$ \ varepsilon_ {2} = \ frac {\ tau} {{k_ {2}}} = \ frac {\ tau f

(5)

#### Viscoelastic housing of various parameters

Zhang et al.^{28} the viscosity coefficient is assumed to be a function of power over time; function *η*_{1}

(6)

where *η*_{10} is the initial coefficient of viscosity of the variable and λ is a constant.

According to the constitutional equation of Kelvin’s material, the creep equation of a variable-parameter viscoelastic body is determined as follows:^{27}:

$$ \ tau = k_ {3} \ varepsilon_ {3} + \ eta_ {1}

(7)

where *τ* is the shear stress of a variable parameter viscoelastic body, *ε*_{3} is the variable parameter viscoelastic body deformation, and *k*_{3} is the modulus of elasticity.

The creep equation of a variable parameter viscoelastic body is determined by integrating the equation. (7) as follows:

$$ \ varepsilon_ {3} = \ frac {\ tau} {{k_ {3}}} \ left[ {1 – \exp ( – \frac{{k_{3} }}{{\eta_{{{10}}} \lambda }}t^{\lambda } )} \right]$$

(8)

####
*Damaged all-plastic housing *

The author presents the damage variable *D*to characterize the degradation of the viscosity coefficient of the creep damage and to construct a viscoplastic housing with respect to the damage. Its constitutional equation can be written as follows^{29}:

$$ \ tau = \ eta_ {2}

(9)

where *τ* is the shear stress of the damaged viscoplastic body,\ (\ dot {\ varepsilon} _ {4} \) is the rate of deformation of the damaged viscoplastic body, and *η*_{2}(*you* ) is a function of the viscosity factor versus time.

Based on the results of many rock creep damage tests, the damage variable *D*took the form of a negative exponential function with respect to time during rock creep^{30,31,32,33,34,35}. In this study, the injury variable is expressed by the equation. (10).

$$ D = 1 – \ exp (- \ alpha t), (0

(10)

where *α*is a coefficient related to the properties of the rock materials.

Based on \ (\ eta_ {2}

(11)

Depending on the nature of the series of components, such a connection can be obtained^{36,37}:

$$ \ varepsilon = \ varepsilon_ {1} + \ varepsilon_ {2} + \ varepsilon_ {3} + \ varepsilon_ {4} $$

(12)

$$ \ left \ {{\ begin {array} {* {20} l} {\ varepsilon = \ frac {\ tau} {{k_ {1}}} + \ frac {{\ tau bt ^ {c}} } {{k_ {20} (1 + bt ^ {c})}} + \ frac {\ tau} {{k_ {3}}} \ left[ {1 – \exp ( – \frac{{k_{3} }}{{\eta_{{{10}}} \lambda }}t^{\lambda } )} \right]} \ hfill & {\ tau <\ tau_ {s}} \ hfill \\ {\ varepsilon = \ frac {\ tau} {{k_ {1}}} + \ frac {{\ tau bt ^ {c}}} {{k_ {20} (1 + bt ^ {c})}} + \ frac {\ tau} {{k_ {3}}} \ left[ {1 - \exp ( - \frac{{k_{3} }}{{\eta_{{{10}}} \lambda }}t^{\lambda } )} \right] + \ frac {{\ tau - \ tau_ {s}}} {{\ eta_ {2} \ alpha}} \ exp (\ alpha t)} \ hfill & {\ tau \ ge \ tau_ {s}} \ hfill \\ \ end {array}} \ right. $$

(13)