A fractional order viscoelastic-plastic creep model for coal sample considering initial damage accumulation

In deep coal and rock mass engineering, extensive initial damage problems caused by excavation and unloading are critical to the long-term deformation and stability of underground projects. An innovative initial damage coal sample test method was proposed, and coal samples with different initial damage were prepared by the MTS pressure tester's circular displacement cyclic loading and unloading control. The creep characteristics of coal samples...