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Abstract The mechanical behavior of rock under cycle load is the one of most important factors which could effect on the long-term stability of rock matrix. So the rock behavior and evolving regular of rock under circulation load are needed to be researched. The samples are selected through the wave velocities of compression wave and shear wave. The rock deformation tests are measured under different confining pressures，constant cycle upper limit confining pressures and triaxial altering confining pressure cycle loading. Triaxial altering confinement pressure cycle test is performed on the GCTS–1 000 rock mechanic test system. The test results are as follows：(1) The deformation of limestone forms a closed plastic sluggish winding when the limestone is loaded or unloaded under altering or constant confining pressure. The areas of plastic sluggish winding diminish succession on the axial deformation；the areas of plastic sluggish winding under altering confining pressure increase succession on the radial deformation；the areas of plastic sluggish winding under constant confining pressure are almost equal. (2) In the triaxial altering confining pressure test，the residual deformation displays a scaling down tendency in condition that the confinement pressure increases and the cycle upper limit stress does not change. The developing trend of axial deformation and radial deformation is contrast to the result of residual deformation. (3) The deformation moduli of cycle loading or unloading progress are different and the deformation moduli of unloading progress are bigger than the value of loading progress. (4) The deformation moduli measured under altering confinement pressure are bigger than the deformation moduli measured under constant confinement pressure. Through experiments，the deformation character and rock elastic parameters of limestone under triaxial altering confinement pressure cycle exist divergence.
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Received: 08 January 2009
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