Dynamics of landslide model with time delay and periodic parameter perturbations

Abstract

In present paper, we analyze the dynamics of a single-block model on an inclined slope with Dieterich-Ruina friction law under the variation of two new introduced parameters: time delay T-d and initial shear stress mu. It is assumed that this phenomenological model qualitatively simulates the motion along the infinite creeping slope. The introduction of time delay is proposed to mimic the memory effect of the sliding surface and it is generally considered as a function of history of sliding. On the other hand, periodic perturbation of initial shear stress emulates external triggering effect of long-distant earthquakes or some non-natural vibration source. The effects of variation of a single observed parameter, T-d or mu, as well as their co-action, are estimated for three different sliding regimes: beta lt 1, beta = 1 and beta > 1, where beta stands for the ratio of long-term to short-term stress changes. The results of standard local bifurcation analysis indicate the onset of complex dynamics for very low values of time delay. On the other side, numerical approach confirms an additional complexity that was not observed by local analysis, due to the possible effect of global bifurcations. The most complex dynamics is detected for beta lt 1, with a complete Ruelle-Takens-Newhouse route to chaos under the variation of T-d, or the co-action of both parameters T-d and mu. These results correspond well with the previous experimental observations on clay and siltstone with low clay fraction. In the same regime, the perturbation of only a single parameter, mu, renders the oscillatory motion of the block. Within the velocity-independent regime, beta = 1, the inclusion and variation of T-d generates a transition to equilibrium state, whereas the small oscillations of mu induce oscillatory motion with decreasing amplitude. The co-action of both parameters, in the same regime, causes the decrease of block's velocity. As for beta > 1, highly-frequent, limit-amplitude oscillations of initial stress give rise to oscillatory motion. Also for beta > 1, in case of perturbing only the initial shear stress, with smaller amplitude, velocity of the block changes exponentially fast. If the time delay is introduced, besides the stress perturbation, within the same regime, the co-action of T-d (T-d lt 0.1) and small oscillations of mu induce the onset of deterministic chaos.