Abstract: To understand the dissolution damage mechanism of the salt cavity surrounding rock in the process of water-soluble cavitation, the high-temperature triaxial dissolution testing machine is applied to conduct tests on salt rock specimens under complex unloading conditions (i.e. unloading confining pressure, increasing axial compression) with different brine flux. It is found that the stress and dissolution influence on each other, and the damage and dissolving characteristics of salt specimens are mutually decide in the process of unloading tests. It is shown that the higher the deviatoric stress is, the greater the amount of dissolved salt rock per unit time is. The outlet concentration of brine exhibits a significant quadratic function relation with the dissolving time. The mechanical strength of salt rock is constantly reduced and its capability of deformation is enhanced under the effect of dissolving. The greater the flux is, the more obvious change trend is. Then, a model of effective dissolving area under the coupled action of stress unloading and water dissolving is set up based on the analysis of effective dissolved area in unloading and dissolution of salt rock. The variation equations of the effective dissolution area with the dissolving time and stress level are obtained respectively. An unloading and dissolving damage evolution equation is established based on the effective dissolving area. The results can provide an important theoretical and experimental basis for further analysis of damage and dissolving mechanism of salt rock.

Key words: salt rock dissolution, stress unloading, brine flux, effective dissolving area, damage evolution