| dc.description.abstract | According to the rock mechanics theory, friction prevents the sliding mass
moving. Furthermore, the slip velocity affectes the friction strength. A lot of
research concentrate on the frictional resistance of the interfaces decreasing while
the sliding rates increase. The importance of velocity-strengthening friction for
numerous elements of frictional events, such as the speed of interfacial rupture
fronts propagating and the quantity of stored energy released by them, has gone
largely unnoticed. A series of experiments are carried out under intermediate slip
velocities (10−7 to 1 m/s) on a sample via low to high-velocity rotary shear
apparatus with the normal stress of 1 MPa. This thesis conducts two different
conditions for shear samples: constant velocity and velocity-step. This study
shows that the steady-state friction coefficient of velocity-step sample is lower
than the one of constant velocity. Comparing the results of this study with the
previous studies, the standard deviation of the steady-state friction coefficient are
relatively large. This study builds velocity-dependent friction model based on the
results of the steady-state friction coefficients of true landslide material and pure
Kaolinite. With the combination of the model and the friction coefficient only
increase without decreasing even the moving mass stops, this study analyzes the
process of creeping landslides on the stability of infinite slopes with parallel
seepage. Although the friction strength of true landslide material and pure
Kaolinite is different, the effect of the height of water table above failure surface
(hw) on results is similar. The investigation results showed that hw significantly
impacts acceleration, velocity, and displacement. If hw > hw-critical, the slope will
keep sliding without stopping so that keeps the groundwater table always below
hw-critical. This thesis considers two cases: 1) If the same model, the maximum
acceleration and velocity increase, especially with the displacement of the sliding
mass significantly rising; 2) if the same hw: a) the maximum acceleration,
velocity, and displacement are larger from Model D-1 to Model D-4 for true
landslide material (Ferri et al., 2011) and from Model W-5 to Model W-8 for pure
Kaolinite, and b) the faster the time duration to reach the peak of the groundwater
table rises, the higher the maximum velocity, the accumulated displacement is
smaller. Using the Newmark method it is possible to establish the relationship
between hw and coefficient of friction in different cases, such as slope geometry
and materials. Thereby setting a landslide warning threshold to assess the
instability of the slope. | en_US |