Abstract: This study is to investigate the effect of the interlayer on mechanical properties and failure mechanisms of salt rock containing interlayers. To overcome the difficulties of field sampling, salt rock samples were prepared in the laboratory for uniaxial and triaxial compression experiments. The experimental results showed that the deformation difference between salt rock and interlayer had a great effect on the mechanical properties of interlayer-bearing salt rock, such as strength and elastic modulus. Under uniaxial compression condition, the fracture failure of salt rock initiated from the interlayer, and then developed into the salt rock layer. It was found that the compressive strength decreased with increasing the interlayer thicknesses. The compressive strength of salt rock samples containing a single interlayer was higher than that of salt rock containing two interlayers. The compressive strength and elastic modulus of salt rock were weakened by the inclined angles of the interlayer. Furthermore, the types of damage in bedded salt rock can be divided into fracture and slippage along the interface between interlayer and salt rock. Under triaxial compression condition, all the compressive strength, elastic modulus and deformation at peak load of bedded salt rock were lower than those of pure salt rock. The pure salt rock demonstrated lateral expansion and failure, and no obvious rupture surface was found. While the mudstone interlayer in the sandwich salt rock showed the characteristics of shear failure, and part of the salt interlayer was lateral expansion. Therefore, this paper can provide helpful guidance to the construction and operation of gas storage caverns in bedded salt rock.

Key words: bedded salt rocks, brittle-hard interlayer, uniaxial compression, triaxial compression, mechanical properties