Experimental Investigations On Impulse Wave Generated By Landslide And Its Propagation Characteristics

Landslide, occurring in large reservoir shore and submarine, may generate huge impulse waves. Generally, this type of wave motion behaves as low frequency and long wavelength. The initially formed impulse waves will propagate long distances and run-up coastline or overtop artificial structures, causing serious disasters and threatening the safety of the adjacent settlements and infrastructures. Hence, the prediction and assessment of the impulse wave characteristics, including the generation and propagation, are of great importance for disaster prevention and mitigation.Through numerical simulations and model tests, researchers have discussed the corresponding variables, which may have significant influence on the impact waves. Some empirical formulae were proposed to predict the primary waveamplitude for different scenarios. To the best of author's knowledge, previous research work was mainly focused on either block landslide or granular landslide, less attention is paid on the combined block-granular landslide model.In the present work, we designed block model, granular landslide and combined block-granular landslide model experiment, respectively. By varying slope angle, slide front angle, granula diameter and mass ration of block model to granular model, this paper experimentally studied the generation, propagation and evolution features of the impulse waves generated by landslide.Firstly, experiments were conducted to research the impulse waves generated by block-slide model. By changing the slope angle and slide front angle, this paper discusses the the primary wave amplitude, wave decay and frequency features. The experimental results show that the primary wave amplitude increases with decreasing of the slope angle while the slide front angle has a complicated effect on the primary wave amplitude under the same water depth and initial release height. In the impact wave zone, smaller main frequency corresponds to the smaller slope angle, and the main frequencies tend to similar to one another with time elapses.Secondly, this paper investigated the impulse waves generated by the granular-land slide model by varying the hill slope angle and granula diameter. The experiment results show that the primary wave amplitude increases with the increase of the granula diameter. However, with the increase of hill slope angle, it is found that the primay wave amplitudes increase with the hill slope angle and then decrease. The wave decay behaves exponentially. When the impulse waves come to steady state, two frequency componnents are presented, and the prequencies and not sentitive to the granular diameter.Finally, based on the research work mentioned above, this paper further more conducted experimental researches on the impulse waves under the combined block-granular landslide. The experimental results are compared with the results of both the blocl-slide model and grunular-slide model. In the past work, most researchers simplified the slide as either block-slide model or granular-slide model, less of works were focused on the impact waves generated by combined block-granular slide model. By varying hill slope angle, granula diameter and the mass ratio of block model to combined block-granular slide model, this paper investigated the impulse waves generated by combined block-granular landslide. The results show that the primary wave amplitudes, generated by the combined block-granula slide model, are larger than that of the block model and granular landslide model. This reveals that the primary wave amplitudes may be underestimated by block-slide model and granular-slide model.