Study on variable parameters model of roadway surroundingrock under influence of unloading

In order to study the stress-strain relationship of rock and the variation of creep model parameters under the influence of different unloading, the sandstone unbalanced unloading creep test was carried out by MTS815.02 Testing Machine. The variable parameter constitutive model considering the unloading quantity was established and compared with the experimental data. The test results show that under the same test conditions, with the increase of the unloading amount of each stage, the difference between the instantaneous strain and the unloading amount also becomes larger. The rock enters the accelerated creep stage more faster and the creep time becomes shorter. The rock deformation eventually becomes larger and the destruction is also more thorough. Based on the test results, the fitting analysis of the creep parameters at each moment of the unloading amount can better reflect the internal damage evolution law and structural deterioration of the rock and describe the stage that was difficult to describe. It shows that the established parametric creep model is suitable and feasible. Meanwhile, the research results provide guiding significance for the surrounding rock support in the roadway and the rock failure during the unloading process.