Shear creep behaviors of sliding-zone soil of bedding landslide in Jurassic stratum in Three Gorges Reservoir area

The creep behaviors of sliding-zone soil play an important role in landslide prediction and long-term stability analysis. The Xingfusi landslide, which is the typical bedding landslide occurring in Jurassic stratum in Wanzhou area, is selected as the study case. The peak and residual shear strength indexes are determined by the triaxial compression tests on the remolding samples firstly, and then the shear creep behaviors of the sliding-zone soil samples are explored by the shear creep tests under different normal stresses and water contents. The results show that: (1) The sliding-zone soil of Xingfusi landslide exhibits the transition from instantaneous creep to attenuation one, and finally keeps a constant creep with a low strain rate before the initial failure. (2) The normal stress shows a negative effect on the strain rate and creep deformation. The shear creep strain at each normal stress is less than 5% before the initial failure. (3) The influence of water content on the strain rate of sliding-zone soil in shear creep is not obvious. The sliding-zone soil has the greatest shear creep modulus when the water content is lower than the plastic limit. As the shear creep proceeds, the shear creep modulis of the samples with low water content or saturated water content have a sharp decrease in short time and then keep a stable value, while the shear creep modulus of the sample with the water content slightly higher than the plastic limit decreases slowly. On the contrary, the shear creep modulus of the sample with water content close to the liquid limit showes a trend of slow increase. (4) The long-term cohesion of sliding-zone soil is 0.70 and 15.0 times the peak and residual cohesions, respectively, and the long-term internal friction angle is 69% and 70% of the peak and residual internal friction angles, respectively. All of the shear strength indexes are affected by the content of fine particles.