Parameters governing debris-flow initiation

A coupled hydromechanical model for deformable porous media with two pore fluids is used to assess the problem of debris-now initiation in slopes. Various ways to identify failure and to approach the transition of the failed mass to a debris now are discussed in the framework of a small strain theory and elastoplastic behaviour. A parametric study was carried out to evaluate the relative importance of the parameters governing debris-now initiation. It was found that the slope angle is of minor importance in the development of slope instability when loading is due to internal water supply. The transient behaviour was found to be decisive and some critical combinations of water supply over time yielded situations likely to be present at the onset of debris flows.