Abstract: For the significant influence of the interface between salt rock and interlayer on the stability and tightness of gas (oil) storage caverns in bedded salt rock, related research of meso and macro-aspects on the fracture properties of the interface has been launched. On meso-aspects, scanning electron microscope(SEM) has been carried out; and the results reveal that the grains embedded with each other very tightly so the cementation near the interface is good; it supplies advantageous guarantee for the tightness of the caverns. On macro-aspect, based on the mechanical theory of composite laminated rocks, the expressions of stresses near the interface of bedded salt rock have been established; and the characteristics of deformation and fracture of interlayer have also been analyzed. The research above indicates that the stress state of the interface is very complex. The anchoring effect of hard interlayer exerting to salt rock has been indicated; and the research also reveals that the stress concentration tends to occur near the interface between hard interlayer and salt rock. Combining the aspects of meso and macro together, the research shows that the mechanism of fracture initiation and propagation, and the formation of percolation paths, are induced by both the meso-structure properties and the macro stress state of the interface. The analysis provides some references for further study of the stability and tightness of storage caverns in bedded rock salt.

Key words: bedded salt rocks, interface, SEM, stress concentration, fracture initiation mechanism, percolation paths