Study on Creep Characteristics and Nonlinear Fractional-Order Damage Constitutive Model of Weakly Cemented Soft Rock

Weakly cemented soft rock (WCSR) strata are widespread in Western China, and their creep characteristics with geo-stress change significantly affect coal mine safety production. To study the long-term mechanical properties of WCSR, creep tests were performed under an initial confining pressure of 0-6 MPa. The results indicated that with a greater initial confining pressure, the WCSR enters the stable creep stage faster. Using the experimental data, a nonlinear damage constitutive model was constructed to describe the creep failure process while considering the residual strength characteristics of the WCSR sample. Each parameter in the constitutive equation was analyzed for its influence on the creep characteristics of the WCSR. It was found that the axial stress, axial deformation, and stable creep rate of WCSR samples entering the stable creep stage under different initial confining pressures are 18.67 MPa, 1.49% and 0.011%/h, respectively. Based on this study, criteria for determining the creep deformation stability of the WCSR roadways and support suggestions are proposed. These findings will aid in further understanding of the creep failure mechanism and control ideas regarding WCSR roadways.