Creep Properties and Constitutive Relation of Anthracite Under Temperature-Stress Coupling

To study the creep characteristics of anthracite under temperature-stress coupling, the muti-functional rock testing machine was used to conduct the tri-axial creep tests under the confining pressure of 20 MPa, the axial pressure of 5 MPa, and the temperatures of 30 ℃, 60 ℃ and 90 ℃, respectively. The results show that the instantaneous strain increases nonlinearly with the increase of temperature. The instantaneous strain at 30 °C, 60 °C and 90 °C is 0.666%, 0.908 4% and 1.272 7%, respectively. The increase of temperature can increase the damage process of deceleration creep and steady state creep of coal. During the creep process of 72 h, the creep strain at 30 °C, 60 °C and 90 °C is 0.503%, 0.581 6% and 0.686 3%, respectively. Based on the nonlinear rheological mechanics theory, a nonlinear viscoelastic-plastic constitutive model is established. According to the creep test results, the model is fitted by curve fitting method. The results show that the anastomosis effect is good, indicating that the model can better describe the creep process of anthracite under temperature-stress coupling.