Abstract: The rheological property of soft rock under water-rock interaction is crucial for the long-term stability of geotechnical projects in real water environment. The creep characteristics of red mudstone in central Yunnan under different stresses and water pressures were studied by means of rock rheological test system under combined action of axial compression and hydraulic pressure. Results unveiled that instantaneous deformation was dominant at low stress level, and the creep curves mainly displayed attenuation and steady stages; accelerated creep stage only appeared at the last stress level. Given the same hydraulic pressure, the instantaneous strain, creep strain and creep rate of mudstone increased with the augment of loading stress; creep characteristics of mudstone are more sensitive to the stress under high water pressure. Under the same stress level, the creep strain, creep rate and the proportion of creep deformation to total deformation of mudstone increased with the climbing of water pressure; such increment intensified under higher stress. The research findings are of engineering significance for ensuring the safety of soft rock project in real water environment.

Key words: red mudstone, creep property, water-rock interaction, combined action of axial compression and hydraulic pressure, rock rheology test