Abstract: By introducing the energy consumption ratio (?), the axial cyclic loading test was carried out to study the energy evolution of sandstones under different confining pressures. The evolution law of ? was analyzed during the full stress-strain process, and then the damage deformation was further explored under cyclic loading. The test results showed that five stages of ? were corresponding to the stages of full stress-strain curves, which were divided into linear decline, stable development, slow increase, sudden increase and gently change, presenting a spoon-shaped evolution feature. It fully reflected the relationship of energy transformation and degree of damage development during the deformation evolution of specimens. In general, the energy consumption ratio (?) reduced as the confining pressure increased. At the same strain level, with the increase of confining pressure, the difference of ? at the stages of linear decline and stable development decreased, then it increased gradually at the stages of slow increase and sudden increase, and finally it decreased to a stable value at the stage of gently change. The variation of material parameters was analyzed, and then a theoretical formula of stress-strain evolution under cyclic loading was deduced by considering the confining pressure and evolution law of ?. The formula was well fitted with test results, which verified its rationality.

Key words: cyclic loading, energy consumption ratio, evolution law, confining pressure, triaxial