Study of Creep Mechanical Properties and a Rheological Model of Sandstone under Disturbance Loads

Xiaofeng Li,Zhixiang Yin

doi:10.3390/pr9081291

Abstract

The stress environments of rock masses are complex. To explore the mechanical properties of sandstone under earthquake or disturbance loads, laboratory triaxial creep tests under different disturbance loads were conducted on sandstone from Fuxin, Liaoning Province, China. Given the disturbance load, a creep deformation pattern for sandstone was analyzed, and the influence of the disturbance load on the mechanical properties of rock was considered. Thus, a constitutive model of rock under creep disturbance load was established. The results show that (1) the creep curve can be divided into four stages: attenuation creep, steady creep, disturbance creep, and acceleration creep; the increment of disturbance creep varies for different disturbance loads and the larger the disturbance load, the larger the disturbance creep deformation; (2) with increasing disturbance loads, the long-term strength, failure time, and elastic modulus of sandstone decreases linearly, while the peak strain increases; and (3) considering the influence of the disturbance load and introducing an acceleration element to modify the Nishihara model, a constitutive model describing the whole deformation process of sandstone under creep disturbance load was established. The accuracy of the model was verified by test data and provides a theoretical basis for rock mass stability analysis.

Highlights

The geological environments of deep rock masses are complex, and the mechanical properties of sandstone and other rocks in deep complex geological environments are different from those in shallow geological environments
To study the rheological mechanical properties of weak rock masses, Liu et al [8] established a nonlinear fractional order creep model of weak rock masses by introducing fractional calculus theory, using the Abel clay-pot element to replace the viscoelastic body in the traditional Burgers rheological model
The influence of disturbance loads on the mechanical properties of sandstone were studied by triaxial compression creep tests under different disturbance loads

Summary

Introduction

The geological environments of deep rock masses are complex, and the mechanical properties of sandstone and other rocks in deep complex geological environments are different from those in shallow geological environments. The long-term deformation characteristics of rock under external load and multifactor coupling conditions are very complex, and the creep model established by the traditional rheological element combination method cannot describe the deformation characteristics of rock well. On the basis of Perzyna’s viscoelastic plastic theory, Jiang et al [7] introduced the meso unit strength damage model of rock based on strain-energy theory, considered the creep. Rate changing with time in the creep process of rock, and constructed a meso viscoelastic plastic damage-coupled creep constitutive model of the whole creep process. To study the rheological mechanical properties of weak rock masses, Liu et al [8] established a nonlinear fractional order creep model of weak rock masses by introducing fractional calculus theory, using the Abel clay-pot element to replace the viscoelastic body in the traditional Burgers rheological model. Fahimifar and Karami [9] modified the viscoelastic plastic model proposed by step to simulate steady-state creep at a low stress level and to calculate creep deformation under repeated loading and unloading conditions

Methods

Results

Conclusion