Experimental study on creep properties of salt rock under long-period cyclic loading

Abstract To study the creep behavior of salt rock under long-period cyclic loading, uniaxial long-period cyclic load creep tests on salt rock specimens under different maximum cycling stresses and periods were carried out. The results indicated that when the maximum cycling stress was greater than 22 MPa, the axial stress-train curve in a single cycle of salt rock could be divided into five stages. When the maximum cycling stress did not exceed 22 MPa and the number of cycles was small, the axial stress-strain curve in a single cycle could still be divided into five stage. However, as the number of cycles increased, stage III gradually disappeared. When a failure occurred, as the number of cycles increased, the maximum creep rate corresponding to the salt rock when it was loaded to the maximum cycling stress showed a trend of “gradually decreasing-basically unchanged-gradually increasing”, and the creep process could be divided into attenuation creep, steady-state creep and accelerated creep stages. When there was no damage, the creep process only included attenuation creep and steady-state creep stages. As the number of cycles increased, the elastic modulus showed a trend of “gradual increase (stage 1)-basically unchanged (stage 2)”. The increment of elastic modulus in stage 1 and the average value of elastic modulus in stage 2 both increased with an increase in the period and the maximum cycling stress. When the maximum cycling stress was the same, there was a critical value for the number of cycles. When the number of cycles did not exceed the critical value, the longer the period, and greater the cumulative irreversible deformation. When the number of cycles exceeded the critical value, the shorter the period, the greater the cumulative irreversible deformation. On the other hand, when the period was the same, the greater the maximum cycling stress, the greater the cumulative irreversible deformation.