Study of red-sandstone post-peak creep test in different loading rates

Due to the complex creep properties on low-strength post-peak rock, a uniaxial incremental loading creep test was conducted on two groups of nine red-sand rock specimens in two loading rates by RLW-2000 rock triaxial rheology test system.The characteristics of post-peak instantaneous and creep strain were analyzed in different stresses, the relationship between instantaneous strength and long-term one was determined, and the basic rock failure morphology was discussed in different stress stages.The results showed that in same loading, the higher the rate was, the smaller instantaneous strain change was; the more the attenuation creep-strain increment was, the smaller the isokinetic one was.With the stress increasing, the instantaneous strain reduced through reducing rapidly, slowly, and then increasing slowly, rapidly, while the post-peak creep strain increased linearly through slowly, average, and then rapidly, which had obviously three stages.The creep failure strength of post-peak rock specimens was similar, the discreteness was small, which was averagely 89.73% of instantaneous one; Instantaneous compress specimen failed in compressing and shearing, and failure rock block was larger.Main post-peak creep failure surfaces were complex:the lower the loading rate was, the more obviously partial specimen was weaken in post-peak creep, and the instability type was mainly compress-shear failure along main fracture surface.