EXPERIMENTAL STUDY ON CREEP BEHAVIORS OF GREENSCHIST SPECIMEN FROM JINPING II HYDROPOWER STATION UNDER BIAXIAL COMPRESSION

The biaxial compression creep tests on greenschist specimens from auxiliary tunnel of JinpingⅡ Hydropower Station were carried out. There were many kinds of loading paths and many different stress levels in the tests. The one-dimensional Burgers model was developed into biaxial compression state. And the creep parameters of greenschist under biaxial compression were determined by Burgers model. The results show that the loading path has important effect on the axial and lateral creep laws. If the axial and lateral loads are exerted simultaneously with fixed ratio,the axial and lateral strains will ascend with increasing axial and lateral stresses. But if the axial load is exerted gradually with fixed lateral stress,the lateral strain will descend with increasing axial stresses. The comparison between Burgers model and experimental curves shows that Burgers model is applicable for determining the viscoelastic rheological parameters of greenschist. These parameters are helpful for the design of deep cavern of Jinping Ⅱ Hydropower Station.