Creep mechanical characteristics and nonlinear viscoelastic‐plastic creep model of sandstone after high temperature heat treatment

Abstract

This work studies the creep mechanical characteristics and nonlinear viscoelastic‐plastic creep model of sandstone treated at different temperatures. The peak strain, uniaxial compressive strength (UCS), and Young's modulus of sandstone treated at different temperatures are discussed as well as creep strain and long‐term strength. The conventional uniaxial compression curves and uniaxial creep curves of sandstone treated at different temperatures are compared. Moreover, a nonlinear generalized Kelvin model is developed to simulate the decay creep deformation; a time‐triggered nonlinear viscoplastic model is proposed to simulate the accelerated creep deformation. By combining the time‐triggered nonlinear viscoplastic model with the nonlinear generalized Kelvin model, plastic element, and viscous element, a nonlinear viscoelastic‐plastic creep model that can well reflect the entire creep process of sandstone treated at different temperatures is established. According to the results of model validation and parameter inversion, the new nonlinear creep model can be employed to predict the creep instability of rocks under high temperature environment.

Creep mechanical properties and creep damage model of sandstone considering temperature effect based on acoustic emission

“…After the temperature rises from room temperature, the natural water in the rock is gradually evaporated, and the lubrication effect of water on the rock crystals is reduced. 11,12,22 At the same time, thermal expansion causes the main cracks in the rock to be compacted and the pores to be contracted. Therefore, as the temperature increases, the UCS of the sample is increased, and the ability of the sample to resist deformation is also improved.…”

“…When the temperature exceeds 600 C, the UCS and Young's modulus of sandstone decrease as the temperature increases. The main reason 22 is that when the temperature exceeds 600 C, the rock sample undergoes phase transformation, and the sliding distance between mineral particles increases, resulting in a decrease in the sample's ability to resist deformation, and the UCS of the sample is also reduced.…”

“…Scholars have proposed various creep models, mainly including empirical models, element models, and creep models based on damage fracture mechanics or fractional derivatives. [18][19][20][21][22][23][24][25] Some creep constitutive models of rocks under high temperature environments have been proposed. For example, Chen et al 26 In summary, although a large number of experiments and theories have explored the creep characteristics of rocks under different temperatures, there is still limited research on the creep failure mechanism of rocks in high-temperature environments, especially the study of creep constitutive models of high-temperature rocks due to the limitations of experimental equipment.…”