A constitutive model of granite shear creep under moisture

Previous constitutive models of granite shear creep have two limitations: (1) although moisture greatly affects granite shear creep behavior, currently there are no constitutive models that include this factor; (2) there are also no models that include an acceleration stage. This paper presents an improved Burgers constitutive model with the addition of a damage parameter to characterize the moisture effect and uses a nonlinear relation equation between stress and strain for inclusion as the acceleration stage. The damage parameter is determined from granite creep experiment under four different moisture contents (0%, 0.22%, 0.49%, and 0.79%). The nonlinear relation equation is obtained by fitting a dataset of stain versus time under five different loading stages. To verify the presented model, a creep experiment was conducted on other granite samples and the results show that the model agrees well with the experimental observation data.