EXPERIMENTAL STUDY ON TRIAXIAL CREEP MECHANICAL PROPERTIES OF SILTSTONE UNDER GRADED LOADING

In order to study the creep mechanical properties of surrounding rock under long-term stress, the triaxial creep test of siltstone was carried out by using zyss2000 creep instrument of high temperature and high pressure of rock of Anhui University of Science and Technology. The creep mechanical properties and model applicability of siltstone were analyzed with Burgers model. The results show that: (1) under confining pressure, rock creep undergoes three stages: (a) decay creep stage, rock shows transient elasticity and then tends to be stable; (b) constant creep stage, rock microstructure continuously reorganizes to reach a dynamic balance; (c) acceleration creep stage, rock weakens and yield failure. (2) Based on the analysis of the viscoelastic plastic strain characteristics of triaxial test, the creep deformation of rock increases with the increase of stress level. (3) Combined with the Burgers model and the test results, the fitting effect is good. The model can better explain the creep characteristics of the roadway under the long-term action, which has a good reference value for the analysis of the long-term stability of the roadway.