Experimental Study on Shear Creep and Long-Term Strength of Clay-Type Muddy Interlayer

In order to have a better understanding of the shear creep characteristics of muddy interlayer in unstable landslides, we took the more "inferior" clay muddy interlayer as the research object, and shear creep experiments under different normal stress levels were carried out by means of hierarchical loading. This paper focuses on the variation law of creep curve and its long-term strength in the clay-type muddy interlayer under different normal stresses. The results showed that the creep characteristics of clay-type muddy interlayer were obvious: at the same normal stress level, instantaneous deformation, initial creep and stable creep appeared at lower shear stress level; at the level of rupture shear stress, there were two cases: the creep curve included three stages of typical initial creep, stable creep and accelerated creep failure, or directly entered the accelerated creep stage until the specimen's failure. The average shear and stable creep rate of the muddy interlayer specimen increased exponentially with the increase in shear stress. The empirical formula u = u0 + A [1 - e(-Bt)] + Ctn of shear strength could better reflect the creep deformation law of muddy interlayer, and the correlation coefficient R2 varies from 0.90 to 0.99. Based on the definition of long-term ultimate strength, the long-term strength of clay-type muddy interlayer was determined.