An improved unsteady creep model based on the time dependent mechanical parameters
Wenbo Liu, Zhang Shu-guang
Abstract
In order to study the obvious rheological properties of the surrounding rock during the mining process of Fuxin Hengda Coal Mine, the creep test under different confining pressures was carried out by using the MTS812.02 test machine. Considering the influence of time and stress on creep parameters and mechanical parameters, a damage model considering time-dependent and stress states was established by introducing the concept of over-stress difference and time product. Based on the Nishihara model, a new unsteady creep model was established. Combined with the experimental results of creep under different confining pressures of sandstone, the parameters in the model were inverted. The parameters obtained were substituted into the model for comparison with the test curve. The results showed that the fitted values from the model matched the creep test data very well. The model could overcome drawbacks in the traditional Nishihara model to describe the accelerated creep phase. This study also presented the deformation characteristics of all three stages of sandstone creep. The results proved that the unsteady nonlinear creep model is reasonable and correct.