Abstract:: In order to study the uncoordinated deformation of different rocks in the salt cavern of China

the conventional uniaxial loading test and Multi-level load creep test on pure rock salt and Salt mud were carried out by using large-scale programmable rheometer of Sichuan University. Based on the tests

the differences of mechanical characteristics between pure rock salt and Salt mud were studied. The results show that the plastic deformation ability and rheological property of salt rock are obviously stronger than salt bearing mudstone. The instantaneous strain generated by loading stress firstly decreased and then increased. Both rocks damaged with the shear characteristic under the condition of long-term creep test

which was different from rocks with the tension damage under the conventional uniaxial. The steady creep rate of salt rock was obviously higher than that of salt bearing mudstone in the same stress percentage and both are exponential function of growth

and the sensitivity of the salt stress is stronger than the salt bearing mudstone. The long-term strength of two kinds of rock was analyzed by using the stress-strain curve inflection point method. The long-term strength of salt rock was 12MPa

which was 48% of short-term compressive strength. The long-term strength of salt bearing mudstone was 34~36MPa

which was lower by 30% than the short-term compressive strength. The ratio of long-term strength and short-term compressive strength of salt rock was much lower than that of most rocks.