Study of the Runout of Granular Columns with SPH Methods
- Xuzhen He (University of Cambridge) | Dongfang Liang (University of Cambridge)
- Document ID
- International Society of Offshore and Polar Engineers
- International Journal of Offshore and Polar Engineering
- Publication Date
- December 2015
- Document Type
- Journal Paper
- 281 - 287
- 2015. The International Society of Offshore and Polar Engineers
- Mohr-Coulomb model, Smoothed-Particle Hydrodynamics, granular flows, Landslides
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- 60 since 2007
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Landslides are catastrophic geophysical phenomena that may cause heavy fatality and property losses. Hence, it is of vital importance to understand their mechanisms and evaluate their travel distance so that appropriate measures can be taken to mitigate their risk. This paper reports on an application of the incompressible Smoothed-Particle Hydrodynamics (SPH) method to the simulation of the collapse of granular columns onto the planes of different slopes, which is similar to dry landslides. Numerical results show that the nondimensional runout is a useful parameter in describing the travel distance as it depends only on the initial aspect ratio. Moreover, the traditional model with a constant friction angle is compared with the modified Mohr-Coulomb model with a variable friction angle sensitive to the shear rate. It is found that the traditional Mohr-Coulomb model with a fixed friction angle is incapable of always predicting the correct runout with different combinations of the aspect ratios and inclined angles. The shear-rate dependence effect must be considered for slim granular columns collapsing onto steep slopes. In addition, the taller granular columns travel much farther than the slowly released columns.
With the growth of population, mountainous areas have been more crowded, where many steep slopes are prone to landslides. When landslides happen, they can claim lives and threaten infrastructure. In addition, they often take place suddenly and move too fast for any mitigation measures to be enacted. Consequently, to quantitatively assess the risk of landslides and properly use the land in mountainous cities, a proper method for predicting the propagation of landslides is necessary. In particular, the prediction of the travel distance of landslides has been a major task for many researchers.
Some researchers predicted the travel distance through empirical-statistical approaches. Unsurprisingly, through these approaches they found that the travel distance depends to some extent on the volume of the landslide mass (Corominas, 1996). As expected, the property of the sliding material also has an influence on the travel distance. Debris flows often show a larger mobility than landslides and rock falls. Furthermore, the dilatancy during the failure process, the geometry of the slope, and the degree of confinement of the travel path should also be taken into consideration when the travel distance is predicted. One limitation of the empirical models is that they are applicable only to the landslides whose conditions are similar to those under which the models are derived. There are also dynamic models that are physically based. These models generally consider the momentum and/or energy conservation of the flow. A widely used continuum-based dynamic model was developed by Savage and Hutter (1989). They incorporated the Mohr–Coulomb model with depth-averaged techniques to construct a set of equations for dry granular flows. As a relatively new computational technique, the Smoothed-Particle Hydrodynamics (SPH) method has been increasingly used for developing the dynamic models.
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