Tsunamis provoked by fast granular landslides: 3D laboratory experiments on generation and initial propagation of waves
- Autores: Francesco Bregoli
- Directores de la Tesis: Vicente César Medina Iglesias (dir. tes.), Allen Bateman Pinzón (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2015
- Idioma: inglés
- Tribunal Calificador de la Tesis: Michele La Rocca (presid.), Juan Pedro Martín Vide (secret.), Enrique Pena González (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Landslides and debris flows falling into reservoirs, natural lakes, fjords or seas can generate impulsive waves, which can be assimilated to tsunamis. This phenomenon, also known as "landslide tsunami", can be highly destructive with respect to dams, other structures and infrastructures as well as to people living along shorelines. The aftermath observation of destructive past events, such as the Vajont Dam in Italy (1963), is not enough to describe and finally to furnish sufficient information to help in adequately preventing the recurrence of the phenomenon. Several authors have carried out experimental studies on the topic in straight channels and wave basins with different landslide generators. Due to the lack of studies on the effects of granular landslides falling in a basin, and in order to explore new ranges of governing parameters for further experiments, the present research work was conceived and undertaken. To this effect, a facility to study that phenomenon was set up in the fluvial-morphodynamics laboratory of the Technical University of Catalonia. The system consists of a steep-slope flume releasing granular material in a wave basin. To achieve a high-speed mass movement, a metallic wheeled box was designed and built, sliding along the flume over rails having a very low surface roughness. The box, filled with gravel, accelerates down the slope. At the end of the run the box¿s flaps open to launch the granular material into the wave basin. A system was designed to be able to measure the high velocity and the geometry of the sliding mass. It employs the treatment of images captured by a high-speed camera which records the granular material at entry into the water. A grid on the water surface was set up employing laser sheets. Thus, by filming the water surface at impact and successively processing the resulting images, it was possible to accurately measure the produced waves. In the present work a number of 41 experiments, changing the main governing parameters, were carried out. The analysis of the experimental results has permitted to define empirical relationships between the landslides parameters and the produced wave amplitude, propagation and energy, as a tool useful for risk assessment. The empirical relationships were successfully tested on two real events: the Vajont Dam (Italy, 1963) and the Chehalis Lake (Canada, 2007). Particularly, the transfer of energy between landslide and water waves was examined. A newel 1D forward Euler model, including the 3D landslide deformations, was created with the aim of measuring the mentioned energy transfer. The result shows that about 52% of the landside energy is dissipated by Coulomb basal friction, about 42% is dissipated by other processes (mainly turbulence) and only the remaining 6% is transferred to the wave train thus formed.
