  Predicting the occurrence of landslides is important to prevent or reduce
loss of lives and property. The stability of rock slopes is often dominated by
one or more locked segments along a potential slip surface; these segments have
relatively high strength and accumulate strain energy. Locked segments can be
preliminarily classified into three categories: "rock bridge", "retaining wall"
and "sustaining arch." Coupling a one-dimensional renormalization group model
with the strain-softening constitutive relation of geo-materials considering
the Weibull's distribution, a physical model for predicting the instability of
slopes with locked segments is established. It is found that the ratio of the
strain or displacement at the peak strength point to that at the volume
dilation point for a locked segment is exclusively dependent on the Weibull's
shape parameter m, and is approximately constant at 1.48. A corresponding
accelerating displacement increment (tertiary creep) of the slope can be
observed from the onset of the volume dilation of the locked segment due to its
unsteady cracking. For a slope with multiple locked segments, one can predict
its critical instability displacement value according to the accelerating
displacement onset corresponding to the volume dilation point of the first
locked segment and the number of locked segments. The back-analysis of two
typical cases, the Yanchihe rockslide in China and the wedge rockslide, Libby
Dam, USA, shows that their evolutionary processes, dominated respectively by
one and two locked segments, follow this model, confirming the reliability of
the proposed model.
