Landslide Motion Prediction by Geotechnical Model Adopting An Apparent-Friction Model

Sassa proposed a geotechnical model to simulate the motion of landslides in 1988 and established the theoretical framework for landslide simulation. By means of finite difference method to solve motion equation on an element in the sliding mass and continuity equation of the entire sliding mass, the thickness change of sliding mass at time steps was simulated. However, the apparent friction coefficient, one of the most important parameter for the calculation should be prepared in advance.

In 2002, based on the experimental results by ring shear tests simulating landslide motion, Wang & Sassa proposed a model for the changing of apparent friction coefficient. In this model, the landslide is considered as a two-layer structure, i.e., debris layer and sliding zone. During landsliding, the debris layer changes its thickness, while the sliding zone changes its shear resistance. Then, a relationship between the apparent friction coefficient and thickness of sliding mass was built. Using the parameter of shear resistance at steady state of the soil from the sliding zone of a landslide, and the effective friction coefficient of the soil, the apparent friction coefficient can be determined for different thickness of the sliding mass.

In this paper, after a brief introduction to the two models and their combination, a parametric study was conducted to show the different importance of each parameter, and the validity of combination of the two models was confirmed. Finally, three case studies (Fei Tsui Road landslide and Shum Wan landslide occurred in Hong Kong in 1995, and Frank slide occurred in Canada 1903) were conducted to show the ability of the combination of the two models for landslide motion prediction.