Study on Creep Mechanical Properties of Red Sandstone in Natural and Saturated States Under Triaxial Compression Condition
Creep mechanical properties as well as long-term strength are considered as the crucial ingredient in the safety evaluation of rock mass engineering in the region of red sandstone.Saturation softening effect plays an important role in creep mechanical properties and long-term strength of red sandstone.Taking red sandstone situating in the site of a dam foundation in Hunan province as the research object,both conventional triaxial compression tests and triaxial creep tests are conducted on natural and saturated red sandstone by the triaxial rock servo-controlling seepage and rheological system V3.The results show peak strength,elastic modulus and creep failure stress decrease due to saturation softening effect,but the degree of their reduction is suppressed by confining pressure.The ratio of creep failure stress to peak strength ranges from 0.75 to 0.98.Instantaneous deformation developed in triaxial creep test is enhanced by saturation softening effect,whereas creep deformation and creep strain rate are weakened.However,the influences of confining pressure on instantaneous deformation,creep deformation and creep strain rate are completely opposite to that of saturation softening effect.The circumstantial strain enters the stable creeping stage and acceleration creeping stage earlier than the axial strain.The relationship of strain rate in stable creeping stage with deviatoric stress can be well described by an exponential function.The long-term strength decreases due to saturation softening effect,but the degree of reduction of long-term strength become small with increasing of confining pressure.The rate of long-term strength to peak strength varies from 0.62 to 0.92.As the crack damage stress is obviously smaller than the long-term strength,it needs further study on the relationship between the crack damage stress and the long-term strength of the red sandstone.
red sandstonecreep propertieslong-term strengthsaturation softening effectcrack damage stress
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