PHYSICAL MODELS OF LANDSLIDES FOR CLASSROOM AND LAB DEMONSTRATIONS

We are developing physical models to compliment any discussion of basic landslide stability calculations. We use dry sand and powder (e.g., flour, dry clay, drywall joint compound) in our models because wet sand is much stronger than dry sand in table-top-scale physical models, and requires us to use waterproof materials. These models can also show internal deformation of the landslide mass during transport and other observable features of natural landslides, although our models are not intended to be perfectly scaled physical models. The models are designed to be made of inexpensive and readily available materials, constructed using common woodworking tools.

All of our current models depict a slice through the middle of a landslide mass, and are bound on the sides by sheets of plexiglass. The upper part of the slip surfaces under the landslides are either smooth mylar or melamine, supported below by wood in which we have cut the appropriate shape of the slip surface. The top surface of the landslide in most of our models is a thin layer of powder, which clearly displays tension and shear fractures. When we run the models, students are able to observe deformation of the top surface as well as internal deformation of the landslide mass through the plexiglass sides of the model.

The first model depicts a simple translational failure due to undercutting of a slope. This type of failure commonly results from "daylighted" conditions that develop as a result of stream erosion, roadcuts or other excavation activities. The second model simulates a landslide moving on a simple cylindrical slip surface, which does not necessarily require the landslide mass to deform internally, except perhaps along the toe of the landslide. The third model depicts a landslide on an irregular slip surface that requires the landslide mass to deform as it moves downslope. Down-slope movement in each of these models can be induced by pulling on a sheet of mylar below the simulated landslide mass. A final model is intended to support discussion of the Taylor method for calculating the stability of a landslide on a spherical or cylindrical slip surface. This model uses sand on a cylidrical slip surface, and the entire model apparatus can be rotated around the central axis of the cylindrical slip surface to change the ratio of driving to resisting forces.