Analysis on time-dependent deformation of landslide based on creep characteristics of weathered red mudstone: A case study of the Luobao landslide in Tianshui of Gansu Province

Creep of weathered red mudstone is one of the important reasons inducing slope deformation and instability in loess plateau of China. Creep constitutive model of weathered red mudstone and time-dependent deformation characteristics of landslide were performed by using the KTL automatic triaxial instrument and CDEM, in giant -scale multiple rotational landslide of Luobao village in Tianshui City. Under different confining pressures between 0.1−0.7 MPa, the stepwise-loading creep tests on weathered red mudstone samples was performed. The creep process and creep characteristics were analyzed. The results show that the samples have experienced instantaneous elastic deformation stage, attenuation creep stage and steady creep stage. Under the same confining pressure, the increment of elastic deformation varies with different stress levels. The increasing rate of deformation is also increased gradually. At a certain stress level, the final creep of the samples under different confining pressures increases gradually with the increase of confining pressures. The increasing rate of deformation is increased slowly. The fitting results show that Burgers creep constitutive model is in high coincidence with the experimental data. On this basis, time-dependent deformation characteristics and the pattern at 1-year scale under gravity stress were revealed by numerical simulation. The results show that almost 95% of deformation occurred within 60 days, and then it entered the steady creep stage. The horizontal displacement of the slide mass decreases with the increase of the depth. The deformation is mainly concentrated on the slide mass Ⅰ, the maximum displacement is about 54.1 cm. The landslide shows a thrust load-caused deformation pattern. Shear strain occurs at the steep-slow junction of the trailing part of each slidemass, the maximum shear strain is about 0.23%, but no transfixion occurred. The whole slope is stable.