Temperature effect on creep of glauberite salt rock under multi-field coupling

In order to study the temperature effect on the creep of glauberite salt rock under tempera-ture-solubility- stress coupling,a self-developed multi-functional rock testing machine was used to conduct the triaxial creep tests un- der the confining pressure of 4 MPa,the axial pressure of 5 MPa,the infiltration pressure of 3,2 and 1 MPa and the temperatures of 30,60 and 90 ℃ . Also,the CT scan of the specimen was performed before and after the test. The effect of temperature on the creep deformation of different creep processes of glauberite salt rock was analyzed. The results show that the main factors affecting the creep deformation characteristics of the glauberite salt rock are the infiltration pressure and temperature in the creep stage of hydraulic connection (CSHC). The smaller the infiltration pressure and the higher the temperature,the greater the creep strain. In the creep stage with pore water pressure ( CSPWP ),the temperature and the effective stress are the main factors affecting creep deformation characteristics. With the increase of temperature,the creep strain gradually increases,and its increment gradually decreases. After 72 h of CSPWP,the creep strain values at 30,60 and 90 ℃ are respectively 0. 009 5×10-2 ,0. 014 4×10-2 ,0. 019 5×10-2 when the infiltra- tion pressure is 2 MPa,and 0. 001 ×10-2 ,0. 003 ×10-2 ,0. 007 ×10-2 when the infiltration pressure is 3 MPa. In the creep stage after drainage (CSAD),the deformation characteristics of glauberite is dominated by the heating damage and the loading history of dissolution under multi-field coupling and the softening degree of mechanical properties of solid skeleton. The creep strain and its increment increase gradually with the increase of temperature. Based on the theory of nonlinear rheological mechanics,the generalized Kelvin model is improved. According to the creep test re- sults,the parameters of the improved model are identified by curve fitting method. The results show that the improved model is appropriate to describe the CSAD under the coupled action of temperature,dissolution and compression.